Official Solution:

The majority of patrons of the local library, though enthusiastic about a new book mobile service, is unable, or either unwilling, to volunteer time to staff it.

A. is unable, or either unwilling
B. is either unable or unwilling
C. are unable, or either unwilling
D. are either unable or unwilling
E. are unable or unwilling, either way,

The sentence is testing the ability to recognize majority as a plural word requiring agreement with a plural verb, as well as the recognition of concision in an either...or phrase.

1. The verb is does not agree with the plural subject majority, and the phrase or either unwilling is unnecessarily wordy.
2. Is does not agree with the plural subject majority.
3. The phrase or either unwilling is wordy and unnecessary
4. The verb are agrees with the plural subject majority, and the rest of the phrase displays appropriate concision.
5. The verb are agrees with the plural subject majority, but the use of either way as an additional phrase is unnecessary and wordy.

Answer: D
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According to MGMAT, Majority is considered as a singular.
Any particular reason for considering it as plural?
explain please

Shouldn't THE MAJORITY be considered singular?
A MAJORITY can be considered plural.

Would someone please explain. Thanks

According to MGMAT,
The words majority, minority, and plurality are either singular or plural, depending on their context. If
you want to indicate the many individual parts of the totality, use a plural verb. If you want to indicate
the totality itself, then use a singular verb form.
The majority of the students in this class ARE hard workers.
In the Senate, the majority HAS coalesced into a unified voting block.

majority of patrons.....patrons require use of "are", instead of the singular is IMO.

I think this is a poor-quality question and I don't agree with the explanation. The majority of patrons should be singular
A majority of patrons is plural

am I right?

If you mean the word to describe a collection of individuals, then the word should be treated as plural. (As in this question)
If the word is used to describe a collective group, then consider it singular.

MGMAT says 'the majority' is singular. Why is plural used here?

Treat such words as "majority", "minority", percentages and fractions, SANAM pronouns similarly. If the noun associated with these quantity words is plural, use plural verb; If the noun associated with these quantity words is singular, use singular verb:

Majority of the students are absent.
Majority of the cake is eaten.

Half of the students are absent.
Half of the of the cake is eaten.

Some of the students are absent.
Some of the of the cake is eaten.

MGMAT says that both usages are possible. Following is an excerpt from the SC guide:

"The words majority, minority, and plurality are either singular or plural, depending on their context. If you want to indicate the many individual parts of the totality, use a plural verb. If you want to indicate the totality itself, then use a singular verb form.

The majority of the students in this class ARE hard workers.
In the Senate, the majority HAS coalesced into a unified voting block."

I think this is a high-quality question and I agree with explanation.

I think this is a high-quality question and I agree with explanation.

Thank you!
I always thought 'majority' is always singular.
Good to know before the actual GMAT!!!!

But in non underline part its written "staff it".So should not be MAJORITY singular ?.

It's not the 'majority' that is plural but the 'patrons' are.
The patrons can do the volunteering and not the majority, hence we need a plural verb here.

The question tests your logical understanding of the meaning.

This is a great question. I was able to understand the correct usage of worlds such as Majority, Minority.....

Thanks everyone.

bçoz it refers to local library ...
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I did the same mistake. Thought 'the majority' is singular and 'A majority' is plural.
From SC grail:
When discussing majority, remember that majority by itself is singular but when it refers to a set of
people, it is plural.
For example:
• A majority is always right.
• A majority of students are right.

Confused majority with 'number'
The number -> Singular
A number -> Plural

According to MGMAT
The words such as majority, minority, and plurality are either singular or plural, depending on their context.
If you want to indicate the many individual parts of the totality, use a plural verb. If you want to indicate the totality itself, then
use a singular verb form.

I think this is a poor-quality question and I don't agree with the explanation. "The Majority of Patrons" should be singular