This one of the key rules to know for both the ACT English Test and the SAT Writing and Language Test. Both of these tests place a strong emphasis on conciseness — namely, that short, clear constructions are preferable to long, wordy ones. When you are given a phrase rewritten several ways, all of which are grammatically correct, the shortest one will virtually always be right.
As a result, you should always start by checking the shortest answer and consider the longer ones only if it clearly does not fit.
Note that this rule applies only to general non-grammar question, NOT ones that require you to give a sentence a particular focus (e.g.” Which of the following most effectively emphasizes the author’s surprise at discovering a frog in her living room?”)
While some incorrect answers will simply include extra, unnecessary words, many others are incorrect because they are redundant.
Incorrect: I decided to ask my mother a question, which required an answer.
Correct: I decided to ask my mother.
The only thing that one can ask is a question; and a question, by definition, requires an answer, so the inclusion of this information is unnecessary.
Incorrect: In 2016, a bright purple ribbon glowed over Alberta, Canada, and the scientists who study aurora borealis—the northern lights—were unaware and did not know that it was even there.
Incorrect: In 2016, a bright purple ribbon glowed over Alberta, Canada, and the scientists who study aurora borealis—the northern lights—were unaware that it was even there.
By definition, people who are “unaware” do not know something, so it is unnecessary to include both.