That comes as a new learning to me. Thanks for the detailed Explanation Jon!!jdenning wrote:Hi kvcpk - thanks for the question. First off, while this question is not actually from the PowerScore course, it is a fantastic illustration of a concept that we cover thoroughly in our course: Collective Nouns in Subject-Verb Agreement. A collective noun is a noun that represents a seemingly plural group/idea, but is in fact singular. Some examples of collective nouns include "jury," "band," "crowd," "flock," "majority," and "dozen." Each of these is treated as singular when used as the subject of a sentence. So you wouldn't say "a jury of Susan's peers are deliberating her guilt," but rather you should say, "a jury of Susan's peers is deliberating her guilt."
For the sentence in question here, answer choice B is correct. The subject of this sentence is "a number," and is therefore singular and requires the singular verb "is." Despite the fact that "a number" clearly refers to more than one reason, it is still considered a singular subject (as it is a collective noun) and attempting to pair it with "are" is incorrect.
Consider another example: "A number of valuables were/was taken by the looters." Again, because the subject of this sentence is "a number" and therefore singular, it requires the singular verb "was." "Was" sounds a bit strange here, I know, but choosing "were" for this sentence is grammatically improper. This is a classic example of why it is so important to familiarize yourself with these commonly tested rules of grammar, and not to simply rely on what sounds best when you take the GMAT!
And one final tip....in the original sentence the phrase "of reasons" is what is known as a prepositional phrase, and prepositional phrases NEVER contain the subject of a sentence on the GMAT. Prepositional phrases are simply given to provide further information about the subject, but they do not contain the subject itself. This is one of the most common grammatical errors tested on the GMAT with respect to Subject-Verb agreement, so please be well aware of it prior to test day!
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