Explanations February



Researchers have long believed that planets form in the disc of gas and dust encircling a young star, but the discovery of planets that are very different from our own may have the potential of turning this theory of solar system formation upside down.


B. in turning
C. for turning
D. to turn


The idiomatic phrase is potential to turn; a preposition + gerund (-ING form) should not be used after this noun. That makes the answer (D).





Bar-tailed godwits have migrated 6,000 miles from Alaska to New Zealand for thousands of years, but a clear picture of their travels have emerged only recently. Today, researchers are beginning to uncover the secrets behind these birds’ remarkable journeys.


B. has emerged
C. emerge
D. emerging


(A) and (C) contain plural verbs, whereas (B) contains a singular verb, indicating that the question is testing subject-verb agreement. In (D), the gerund emerging creates a fragment, so it can be eliminated immediately. What is the subject of the underlined verb — that is, what has emerged only recently? A clear picture of their travels. Don’t get distracted by the plural noun travels, which appears right before the verb. That noun is part of the prepositional phrase of their travels. The subject is A clear picture or, more precisely, picture. That noun is singular, so a singular verb is required. Only (B) contains a singular verb (has emerged), so it is correct.





Take a look at some of the flowers photographed by Carol Sharp, and you might feel as if you’ve suddenly been transported into an alien world. In Sharps’ pictures, pigmented petals contrast starkly with a black background, while specks of light scatter across the blossoms.


B. Sharp’s
C. Sharps’s
D. Sharps


The first sentence indicates that the photographer in question has the name Carol Sharp, and the context of the following sentence makes clear that the name must be possessive — it is referring to her photographs. The apostrophe rules that apply to nouns in general also apply to names: to make a name plural, add apostrophe + -s. That makes the answer (B). In (A), -s + apostrophe is used for plural possessive names (e.g., the Sharps’ house = the house belonging to the Sharps). In (B), Sharps’s would be the possessive of the singular name Sharps. And in (D), Sharps would simply be the plural of the last name Sharp (e.g., the Sharps are home tonight = the Sharp family is home tonight).





Formed by volatile chemical compounds that rapidly disintegrate, odors are often fleeting and rapidly disappear, remaining only in people’s memories.


B. fleeting, disappearing rapidly,
C. fleeting so that they disappear rapidly,
D. fleeting,


By definition, something that is “fleeting” disappears rapidly, so (A), (B), and (C) all contain redundancies. Only (D) eliminates that problem, making it the answer. Note that even if you do not know the definition of fleeting, you can still make a very educated guess that (D) is correct just by looking at the answers. Questions with this type of answer pattern are virtually always testing wordiness, so given three lengthy answers and one short one, the short one will almost certainly be correct.





In 1610, the year Galileo began viewing the sky through the lens of a telescope, he had become the first person to observe Saturn’s rings directly.


B. has become
C. would become
D. became


The past perfect (had become) should only be used to describe an event in the past that took place before a second event in the past. Logically, however, Galileo could not have become the first person to view Saturn’s rings before he began viewing the sky through a telescope. That eliminates (A). (B) is incorrect because the present perfect (has/have + verb) is used to indicate an action that began in the past and is continuing into the present. As the date 1610 makes clear, however, Galileo’s initial viewing of Saturn’s rings occurred long ago. (C) is incorrect because would is used to refer to a hypothetical action — one that could occur — whereas the sentence is describing an action that did in fact occur. (D) is correct because simple past (became) is used to describe a finished action in the past. Because the other verb in the sentence is in simple past form as well (began), this answer also maintains parallel structure.





Because fairs often attracted large and uncontrollable crowds, permission to hold one could only be granted by royal charter during the Middle Ages.


(B) Because they often attracted large and uncontrollable crowds, permission to hold a fair could only be granted by royal charter during the Middle Ages.
(C) Having often attracted large and uncontrollable crowds, it could only be permitted for a fair to be held by royal charter during the Middle Ages.
(D) Often attracting large and uncontrollable crowds, during the Middle Ages fairs could only be permitted by royal charter.


In (B), the introductory clause because they often attracted large and uncontrollable crowds can only describe fairs, the subject. As a result, fairs must be placed immediately after that clause, following the comma. It is not placed there, however, so this answer creates a dangling modifier. (C) and (D) contain the same error: both begin with introductory phrases that describe fairs, but neither places that word immediately afterward. The original version avoids the dangling modification by placing fairs at the beginning of the sentence. (A) is thus correct.





In the last few years, some towns in Iceland, India and China have experimented with “floating” cross walks. They rely on three-dimensional optical illusions for their effectiveness, they make the crossings appear to be floating above the ground, thus causing drivers to slow down.


B. Relying on
C. These rely on
D. Although they rely on


If you just focus on the beginning of the sentence, then the construction in the original version seems perfectly acceptable; the problem isn’t apparent until later in the sentence. The comma after effectiveness creates a comma splice: two complete sentences separated by a comma. Because they make cannot be changed, the construction at the beginning of the sentence must be changed instead. (C) creates the exact same error as (A) — they and these are grammatically interchangeable, so this answer does nothing to address the actual problem. (D) is grammatically acceptable — placing although at the beginning of the sentence makes the first clause dependent and thus able to be separated from the rest of the sentence by a comma — but it creates an illogical relationship: there is no contrast between the fact that “floating” cross walks rely on optical illusions and that they appear to float. (B) is correct because the use of an -ING word (relying) rather than subject + verb (they rely) creates a dependent clause without disrupting the logic of the sentence and makes the comma after effectiveness acceptable.





If you had stepped off a plane in Bogota, Colombia, in the 1960s, one of the first things you would of probably saw outside the airport was a giant billboard. In a slightly menacing tone, it said, “Coffee rust is the enemy. Don’t bring plant materials from abroad.”


B. would of probably seen
C. would have probably saw
D. would have probably seen


As a rule, would (along with could, should, and might) must be followed by have, not of — this very common error plays on the fact that the two words are pronounced identically. Because the correct answer must contain have, both (A) and (B) can be eliminated. (C) can be eliminated as well because any form of the verb have must be followed by the past participle (seen) rather than the simple past (saw). (D) provides the correct form and is thus the answer.





Enabling workers as well as pedestrians to walk in climate-controlled comfort even when temperatures drop well below zero, and the Minneapolis Skyway System is an interlinked collection of enclosed footbridges that connect various buildings over 11 miles of downtown Minneapolis.


B. zero, but the Minneapolis Skyway System
C. zero, the Minneapolis Skyway System, which
D. zero, the Minneapolis Skyway System


(A) and (B) are incorrect because comma + and & comma + but are used to separate two complete sentences; however, the statement before the comma (Enabling workers as well as pedestrians to walk in climate-controlled comfort even when temperatures drop well below zero) is not a sentence. (C) fixes the original problem but creates a new one: it turns the main clause into a fragment. The addition of comma + which “removes” the verb is from its intended subject, the Minneapolis Skyway System, and makes which the subject. As a result, the clause lacks a main verb. The only grammatically acceptable option is (D), which correctly places a comma alone between a fragment and the full sentence that follows.





Cheetahs are known for their impressive running speeds, which can reach more than 60 miles per hour. Lions are more powerful. However, they are not nearly as fast on their feet.


Which of the following would NOT be an acceptable alternative to the underlined portion?


A. powerful, but they are
B. powerful; they are, however,
C. powerful but
D. powerful, but are


The question is asking which option would NOT be an acceptable alternative to the underlined portion, so the correct answer must be grammatically incorrect. (A) can be eliminated because comma + but is grammatically equivalent to period + However, which appears in the passage itself. (B) can be eliminated because this answer is also grammatically equivalent to the version in the sentence — the words are just rearranged. A period is identical to a semicolon, and however is merely moved to a later point in the clause. In terms of meaning, there is no difference between beginning a sentence/clause with a transition, and surrounding that transition with commas later on in the sentence. Both versions indicate that the transition is connecting that statement to the previous one. (C) is okay as well because there is no reason to use any punctuation before but. A semicolon or period is never correct before this word, and comma + but is identical to a period. It would make no sense to say Lions are more powerful. Not nearly as fast on their feet. That leaves (D), which incorrectly places a comma before but. Again, comma + but = period, and it does not make sense to plug in a period: Lions are more powerful. Are not nearly as fast on their feet. Because (D) is NOT acceptable, it is correct.





The “Ring of Fire” is a string of volcanoes, earthquake sites, and tectonic plates around the Pacific. It spreads across 25,000 miles, from the southern tip of South America all the way to New Zealand. Roughly 90% of all earthquakes occur in the ring, with the majority of those quakes resulting from a small number of locations where plates are exceptionally active.


B. along with
C. in addition to
D. and


To answer this question, you need to focus on the section of the sentence that comes after the underlined portion. The most important thing to notice is that it contains an -ING word (resulting) rather than a conjugated verb (result). If you know that the construction with + -ING can be used as an alternative to and + verb (e.g., and the majority of quakes result from…), then you can focus on (A) from the start. Both (B) and (C) can be eliminated because they create awkward, illogical constructions when plugged into the sentence. Note that although with + -ING is a common idiomatic construction, along with cannot be used as an alternative. (D) is incorrect because a clause that begins with a conjunction (and) and contains a subject (the majority) must contain a verb rather than an -ING word. That leaves (A), which is correct.





At least in moderate amounts, stress may not be as harmful as we think. In fact, research suggests that people who view stress as a form of motivation perform better under pressure and have less health complaints than those who view stress as debilitating.


B. less health complaints then
C. fewer health complaints than
D. fewer health complaints then


To answer this question, you need to know that less is used to modify singular nouns, whereas fewer is used to modify plural nouns. Health complaints is plural, so fewer should be used. That eliminates (A) and (B). (D) can be eliminated as well because then is a synonym for nextthan is used for comparisons. (C) provides the correct form, making it the answer.





In a downtown park in the city of Kumamoto on Kyushu, the southwestern-most of Japan’s main islands, a group of locals can be found trying consistently to complete what could be called the world’s hardest jigsaw puzzle. It’s a problem so large that the pieces cover the size of a football field, a riddle so challenging that it will take them nearly 20 years to complete.


Which choice most strongly emphasizes that the group is focusing intently on the puzzle?


B. painstakingly
C. excitedly
D. impulsively


The key phrase in the question is focusing intently, so the correct answer must be consistent with the idea of intense concentration. Consistently just means “on a regular basis” — it has nothing to do with the amount of focus an action is performed with. (A) can thus be eliminated. If you don’t know what painstakingly means, skip it and work through the other options. Excitedly might seem like a possible answer, but be careful: being excited about something is not necessarily the same thing as paying very close attention to it. The two things can be related, but one does not automatically imply the other. Impulsively means “without warning,” or “on the spur of the moment.” Again, this is unrelated to the idea of intense focus. That leaves (B). To do something painstakingly is to do it with enormous care and attention to detail, i.e., to focus on it intently. That makes (B) the answer.





Citrus trees are among the most widely cultivated fruit trees in the world, but until recently, their history has been unclear. Seeking to obtain a better understanding of where these trees originated, the genomes of more than 50 varieties of citrus fruit were analyzed by researchers in the United States and Spain, from the Chinese mandarin to the Seville orange.


B. an analysis of the genomes of more than 50 varieties of citrus fruit was performed in the United States and Spain by researchers,
C. more than 50 varieties of citrus fruit had their genomes analyzed by researchers in the United States and Spain,
D. researchers in the United States and Spain analyzed the genomes of more than 50 varieties of citrus fruit,


The key to answering this question is to consider the answer in relation to the beginning, non-underlined portion of the sentence. Approached that way, this question is much simpler than it appears. Who was seeking to obtain a better understanding of where these (citrus) trees originated? Logically, it could only be scientists. So scientists, the subject, must be placed at the beginning of the correct option. Placing the genomes, an analysis, or more than 50 varieties in the spot creates a dangling modifier. That makes (D) the only possibility. Note that this option also fixes the modification at the end of the sentence. The last phrase, from the Chinese mandarin to the Seville orange, refers to types of citrus fruit, so citrus fruit must be placed at the end of the correct option, right before the comma.





Creativity is often defined as the ability to come up with new and useful ideas. Like intelligence, it can be considered a trait that everyone, not just creative geniuses possesses in some capacity.


B. geniuses that possess
C. geniuses possesses,
D. geniuses, possesses


The key to answering this question is to recognize that the verb possesses belongs to the subject everyone, which appears in the non-underlined portion — possesses is singular and cannot agree with the plural noun geniuses. The only way to make everyone the subject of possesses is to create a non-essential clause. The first comma appears after everyone, and the second comma must appear before possesses. When the clause is crossed out, the remaining sentence makes perfect sense: …it can be considered a trait that everyone…possesses in some capacity. That makes the answer (D). When the comma is placed after possesses, as is the case in (C), the remaining sentence does not make sense: ...it can be considered a trait that everyone… in some capacity. (A) and (B) are in part incorrect because they do not create a non-essential clause at all. In (A), the singular verb possesses also directly disagrees with the plural subject geniuses. Although the phrase geniuses that possess in (B) is acceptable on its own, it creates an awkward and ungrammatical construction when it is plugged into the sentence.





The origins of saffron are a mystery: competing claims place the wild plants beginning’s in regions along a wide swath of land, from Greece in the eastern Mediterranean all the way to Central Asia.


B. plants beginnings
C. plant’s beginnings
D. plant’s beginnings’


Don’t get too thrown off by all the different combinations of plural (-s only) and possessive (apostrophe) forms. When two nouns are underlined, the usual pattern is that the first noun has an apostrophe but the second does not. As a general rule, when two nouns are placed next to each other without a comma between them, the first is possessing the second. That eliminates (A) and (B). To confirm that the second noun does not require an apostrophe as well, look at the word after beginnings. In is not a noun, so beginnings does not require an apostrophe. That eliminates (D), leaving (C). wild plants beginnings = beginnings of the wild plant, i.e., the origins of saffron.





At any given time, the vast majority of the volcanic activity on Earth isn’t occurring in continent-covering floods of magma or in explosions like the one at Mount St. Helens. Rather, it’s on the seafloor, where the tectonic plates are spreading apart. As the Earth’s crust splits, the mostly solid mantle layer raises to fill the space created.


B. raises for filling
C. rises to fill
D. rises in filling


When used as a verb, raise must either be followed by a noun (e.g., they raise chickens on their farm) or used as part of a passive construction (e.g., wages were raised). It is incorrect to say x raises — when no noun is present right after the verb, the correct form is rises. In this case, the underlined verb is not followed by a noun, so rises should be used. In addition, this verb must be followed by an infinitive (to fill) rather than in + -ING. That makes the answer (C).





The fight between the Earth’s magnetic field and the solar wind produces some surprising effects, including: the Aurora, or the Northern and Southern Lights, which can appear when the highly charged particles from the sun hit the Earth’s atmosphere, causing a glowing green light display.\


B. effects, including the Aurora, or the Northern and Southern Lights,
C. effects, including the Aurora, or the Northern and Southern Lights;
D. effects including the Aurora or the Northern, and Southern Lights


Although colons are used to introduce lists and explanations, they should not be placed after the word including. The reason is that a colon must be preceded by a sentence that can stand on its own as a complete thought, a construction that is essentially impossible when a statement ends with including. Here, for example, The fight between the Earth’s magnetic field and the solar wind produces some surprising effects, including clearly cannot stand by itself. That eliminates (A). (C) is incorrect because when this answer is plugged in, the semicolon is placed between a sentence and a fragment rather than two complete sentences. Note that the semicolon is immediately followed by which, a word that cannot begin a sentence. (D) is incorrect because including should be set off by a comma and because no comma should be placed before the word and. Comma + and = period, and it makes absolutely no sense to say …effects including the Aurora or the Northern. Southern lights which appear.… (B) appropriately uses a comma to set off including, and the commas around or Northern and Southern Lights also correctly signal that this phrase can be removed from the sentence without disrupting its basic grammatical structure: The fight between the Earth’s magnetic field and the solar wind produces some surprising effects, including the Aurora…which can appear when the highly charged particles from the sun hit the Earth’s atmosphere, causing a glowing green light display.





It is well known that seismic activity can affect hydrologic activity—that is, the movement of water. In the aftermath of nearby large earthquakes, dry streams can start flowing, well levels can go up or down, and eruptions of geysers sometimes occur.


Which choice best maintains the pattern already established in the sentence?


B. sometimes geysers will erupt.
C. geysers can sometimes erupt.
D. there is an eruption of geysers sometimes.


The first two items in the list both contain the structure x can do y (dry streams can start flowing, well levels can go up or down), so the third item must be presented in that structure as well. The fastest way to answer this question is to notice that (C) alone contains the word can. That makes it the only possible answer.





Generally speaking, solar eruptions are caused by a sudden, violent rearrangement of the Sun’s magnetic field. At a deeper level, however, the process is controlled by two types of structures that form in the magnetic field of the Sun: ropes and cages. The rope is confined within the magnetic cage. If the cage is strong, it can contain the rope’s contortions, but when the cage is weak, an eruption can cause it to rip through.


As it is used in the last sentence, the word “contain” most nearly means


A. encompass
B. restrict
C. exclude
D. comprehend


In the last sentence, the word but sets up a contrast between what happens when the cage is weak (an eruption can cause it to rip through) and what happens when the cage is strong. Logically, the sentence must be saying that when the cage is strong, it must prevent the rope from ripping through, or cause it to remain within the cage — in other words, it must restrict the rope. The answer is therefore (B). Don’t get distracted by encompass — this is a literal synonym for contain, but it doesn’t have the same connotation of preventing something from breaking through. Be careful with (C) as well: exclude implies that the cage stops the rope from contorting at all, not that it limits the rope’s movement. In addition, this word has the wrong connotation: it implies that something or something is not allowed to participate in a group or event, a meaning that does not make sense here. Comprehend does not fit at all.





Scientists have found that animals across the spectrum have a keen sense of quantity, able to distinguish not just bigger from smaller or more from less, but two from four, four from ten, and forty from sixty. Orb-weaving spiders, for instance, keep a tally of how many silk-wrapped prey items are stashed in the “larder” segment of their web. In one experiment, scientists removed the items. Despite this, the spiders spent time searching for the stolen goods in direct proportion to how many separate items had been taken.


B. Subsequently,
C. However,
D. Likewise,


Start by ignoring the transition already in the passage, and focus on determining the relationship between the sentence begun by the underlined transition and the sentences before — to make sense of this question, you must consider the last sentence in terms of the full paragraph. Essentially, the passage is discussing the fact that animals are capable of identifying specific quantities, and orb-weaving spiders are used as an example of a species that can apparently keep track of specific numbers. The “experiment” is then cited to explain how scientists determined orb-weaving spiders possessed that ability. The last sentence of the passage describes the result of the experiment: the spiders’ behavior suggested they could in fact count. Given that context, the correct transition must indicate that the last sentence is continuing the idea presented before it. Despite this and However are used to introduce contrasting ideas, so (A) and (C) can be eliminated. Even though likewise is used to introduce similar ideas, it does not fit here. This transition indicates that two things are similar, or like one another, which is not the case here — the last sentence focuses on the spiders’ behavior, whereas the previous sentence describes the scientists’ action. The only option that makes sense is subsequently, which means “next” or “then.” Logically, the spiders spent time searching for the stolen goods after the scientists removed them. That makes (B) the answer.





Whatever the truth behind the origins of macaroni and cheese, this humble dish has become an ultimate comfort food in many cultures and countries, each with their own favored variations.


B. they’re
C. its
D. its’


Don’t get distracted by the plural nouns countries and cultures — the underlined pronoun refers to each, which is singular (each is short for each one) and thus requires a singular pronoun. Their and they’re are forms of the plural pronoun they, so (A) and (B) can be eliminated. (D) can be eliminated as well because its‘ does not exist. That leaves (C), which correctly provides the singular possessive form, its.





All frozen water consists of molecules arranged in a hexagonal structure similar to a honeycomb; however, the ice coating bobsled tracks or the firm, flattened snow of a ski course is precisely shaped and conditioned, optimizing the properties of this frosty form of water.


B. firm, flattened, snow of a ski course
C. firm flattened snow, of a ski course
D. firm, flattened snow of a ski course,


All of the answers might look similar initially, so try to avoid letting them blur together, and instead focus on finding the differences in the placement of the commas. There are a few key features here that can help you eliminate incorrect answers quickly. (B) can be crossed out because commas can be placed only between adjectives (firm, flattened), never between an adjective and the noun it modifies (flattened, snow). If you know the “no comma before a preposition rule,” (C) can be eliminated because a comma is placed before the preposition of. Note that the lack of a comma between firm and flattened is only a distraction here. Be careful with (D): when this answer is plugged in, a comma is placed between the subject and the verb (the firm, flattened snow of a ski course, is precisely shaped...). This construction is never correct, so (D) can be eliminated too. That leaves (A), which correctly places a comma between the two adjectives (firm and flattened) and does not contain any additional, unnecessary punctuation.





The appearance of tiny cracks in concrete can be harmful because they provide an easy route of entry in for liquids and gasses – and the harmful substances they contain. Even a slender breach the width of a hair can let enough water in to undermine the concrete’s integrity. For example, micro-cracks can allow water and oxygen to infiltrate and then corrode steel supports, causing a structure to collapse.


If the author were to delete the underlined portion, the paragraph would primarily lose


A. a detail that emphasizes the dangerous consequences of tiny imperfections in concrete.
B. a claim that shifts the paragraph away from the discussion of harmful substances.
C. a comment that introduces the main idea of the paragraph.
D. irrelevant information that distracts from the focus of the paragraph.


Although the question appears to ask about the paragraph without the underlined phrase, this wording is somewhat misleading. In reality, the question is asking what sort of information the underlined phrase contains. As a result, you should start by focusing on the phrase itself. The first thing to notice is that it contains a description: it illustrates just how small a “slender breach (crack)” can be. A description isn’t a “claim,” as (B) states. It’s also smack in the middle of a sentence, so it can’t really be a comment introducing a main idea, as (C) indicates. The fact that the phrase provides detail can point you to (A). Something that is the width of a hair is very, very small. The next sentence indicates that these tiny cracks can [cause] a structure to collapse, and so the underlined description emphasizes just how seriously concrete can be affected by apparently minuscule flaws. Far from being irrelevant to the point of the paragraph, this information serves to reinforce it. That eliminates (D) and makes the answer (A).





Maglev—or magnetic levitation—trains, which use magnets to lift a train above its rails, reducing friction, and increasing possible speeds are already in operation. The most famous one takes passengers from downtown Shanghai to the city’s airport at 270 miles per hour. But of the plans to make a maglev even faster by putting it in a vacuum tube, Hyperloop One is the most advanced.


B. reducing friction, and to increase possible speeds,
C. reducing friction and increasing possible speeds,
D. reduce friction, and increasing possible speeds


This is a question that initially seems to be testing parallel structure in list form but then throws in a twist. The non-underlined portion of the sentence contains the first item (to lift a train above its rails), so the second and third items would logically be (to) reduce and (to) increase. The problem is that there is no option with this construction. (B) and (D) contain various combinations of -ING words, verbs, and infinitives, none of which works grammatically, so they can be eliminated. That leaves (A) and (C), the only answers that contain verbs in parallel form (reducing, increasing). (C) is correct because it creates a non-essential clause rather than completing a list. You can check this out by crossing the clause out of the sentence: Maglev trains, which use magnets to lift a train above its rails,…are already in operation. The sentence that remains makes grammatical sense, so this answer is acceptable. (A) does not work because there is no comma after speeds, so this answer cannot function as a non-essential clause. As a result, it creates yet another non-parallel list.





A new type of vaccine, which could become available in the United States over the next few years, is made by growing viruses in cultures of animal cells rather than with chicken eggs.


B. in
C. to
D. from


The sentence contains the basic structure A new type of vaccine is made by growing viruses in x rather than ______ y, so the prepositions on either side of the phrase rather than must be the same in order to create a parallel construction. The preposition on the non-underlined side of the sentence is in, so the same preposition must be used in the underlined portion as well. That makes the answer (B).





A factory needs robots to perform repetitive tasks at high volume 24 hours a day. The most common robots are large industrial machines dedicated to specific processes that run independently and can be more than six feet tall and 30 feet long.


B. processes, which run independently and can be
C. processes. These machines run independently and can be
D. processes; running independently and being


The original version contains a misplaced modifier: the phrase that run independently and can be [more than six feet tall and 30 feet long] should logically describe large industrial machines but instead describes specific processes — clearly processes cannot be six feet tall and 30 feet long. (B) contains the same error; this answer just uses which instead of that to begin the modifying phrase. (D) is incorrect because a semicolon must be used to divide two complete sentences, and running independently and being more than six feet tall is not a sentence. As a shortcut, a semicolon should not be followed by an -ING word. Although it is longer than the other answers, (C) is correct because it eliminates the misplaced modification by making clear that more than six feet tall and 30 feet long describes industrial machines and uses a period to divide two complete sentences.





Sleep-inducing substances may come from the process of making new connections between neurons. Sleep researcher, Chiara Cirelli, suggests that since making these connections, or synapses, is what our brains do when we are awake, maybe what they do during sleep is scale back the unimportant ones, removing the memories or images that don’t fit with the others, or don’t need to be used to make sense of the world.


B. researcher, Chiara Cirelli
C. researcher Chiara Cirelli,
D. researcher Chiara Cirelli


When it comes to commas with names in the middle of a sentence, there are essentially two options: no commas (essential) or two commas (non-essential). A comma only before the name is always incorrect, and although a comma only after the name may in extremely rare cases be acceptable, this is not an exception that you normally need to worry about. The easiest way to check whether commas are necessary is to cross the name out and read the sentence without it: Sleep researcher…suggests that since making these connections, or synapses, is what our brains do when we are awake… No, that does not make sense. Although it may be grammatically acceptable in the most technical sense, it not only sounds completely wrong but it also does not tell us who the sleep researcher is. The name is therefore essential for the logic of the sentence. As a result, no commas should be used, making (D) correct.



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