When the clause Mount St. Elias stands over 18,000 feet tall is crossed out, the sentence still makes sense (It showcases towering mountains…as well as glaciers), so the clause is non-essential. A dash is used to signal the beginning of the non-essential clause, so it must be used to mark the end as well.
If you’re not sure about A), play process of elimination: although B) is grammatically acceptable because there is a complete sentence on either side of the semicolon, the phrase lengthy driving day is awkward and unidiomatic. C) is incorrect because the two halves of the sentence express similar ideas, indicating that but should not be used. D) is incorrect because its is possessive; it’s must be used instead (It is a long day’s drive). That leaves A), which correctly uses a dash to create a stylistic pause before the second half of the sentence.
As a rule, no colon should be used after such as, even if a list is involved. That eliminates A) and D). B) can be eliminated as well because a comma is used between the second and third items in the list (examining x-rays, and applying protective sealant), and semicolons and commas should not be mixed within a list. C) correctly eliminates the unnecessary punctuation after such as and retains the comma after the first item in the list.
The clause who receive medical training similar to that of doctors is non-essential because the sentence still makes sense without it (Dentists can also perform oral surgery on patients and write prescriptions). The beginning of the clause is set off by a comma, so a comma—and not a dash—must be used to end it.
To answer this question, you must read the entire sentence, not just the underlined portion. The dash is used to signal the beginning of a non-essential clause (which is taking root among some of the world’s most powerful corporations), but a comma is used to mark the non-underlined end. As a result, the dash at the beginning must be changed to a comma.
Because The system works by is not a sentence, a colon should not follow it. That eliminates A). D) creates the same error, swapping a colon for a dash. B) is incorrect because this answer incorrectly places a comma before a preposition (by). C) correctly eliminates the unnecessary punctuation after by.
The original version correctly places a colon after a complete sentence and before an explanation. B) is incorrect because its rather than it’s should be used (you would not say, it is head tapers to a point). C) is incorrect because it contains a comma splice (tip-off comma + its). D) is incorrect because it places two sentences back-to-back without any punctuation between them (fused sentence).
The phrase perhaps a mad scientist is non-essential because the sentence still makes sense when it is crossed out (its head tapers to a point, making it look as if someone…had grafted a snake’s head and several inches of scaly body onto a fish). Because a dash is used to mark the end of the non-essential phrase, a dash should be used at the beginning as well.
Comma + and in A) and the semicolon in D) are grammatically identical, so both of those answers can be eliminated immediately. B) can be eliminated as well because some type of punctuation is required before the nickname. C) correctly places a colon after a complete sentence and before a single-word explanation/definition.
The clause pictures made of many small pieces is non-essential because the sentence still makes sense when it is removed (The appearance of mosaic murals…has remained unchanged for thousands of years). A dash is used to signal the end of the non-essential clause, so a dash must be used at the beginning as well.
Colorful, three-dimensional stone walls murals is not a complete sentence, so it should not be placed after either a period or semicolon. A) and D) can thus be eliminated. B) can be eliminated as well because some type of punctuation is required to separate the phrase colorful, three-dimensional stone walls from the independent clause that precedes it. C) is correct because the colon follows a complete sentence and introduces an explanation of what the new style is.
A) is incorrect because a colon must follow a complete, standalone sentence, and She combined the piecework of mosaic murals with traditional soapstone slab carving to produce cannot stand on its own as an independent thought. C) creates the same error, replacing the colon with a grammatically equivalent dash. B) is also incorrect because a complete sentence must follow a semicolon, and lifelike tropical plants, flowers, and sea life scenes ranging in size from a few inches to life-size plants inlaid along entire walls is a fragment. D) correctly omits the unnecessary punctuation after produce.