Answer:
b. Believes.
Explanation:
Subject-verb agreement refers to the use of the same number for the subject and the verb used. In other words, the subject-verb agreement means the subject and the verb are the same in number, meaning a singular subject will have a singular verb, a plural subject will have a plural verb, etc.
In the given sentence, the subject is "neither of my little brothers". This means it is a singular subject, referring to none of the brothers. Thus, according to the subject-verb agreement, the verb will be in the singular too.
Therefore, the correct sentence will be
Neither of my little brothers <u><em>believes</em></u> in Santa Claus.
