A student asks the English Master to settle a dispute:

Please answer this grammar question for me:

Neither my brother nor my sister ______ ever visited the White House.
a. have
b. has
c. is
d. are

If you answer it, please explain why. There is a battle on our school grounds as to what the correct answer is. Thanks for the help.

The correct answer is…drumroll please…”b. has.” Here’s why:

We can eliminate “c” and “d” immediately because they don’t make sense grammatically. Then, to determine whether the appropriate verb is have or has, we need to make sure that the verb “agrees” with the subject in number. This task is relatively easy when the subject is a single word: The house is on fire. When we’re confronted with an “either/or” or “neither/nor” construction, we need to go with the noun that is closer to the verb (in this case, “sister”). That’s because we’re only referring to one or the other, the sister or the brother, but not both. If, on the other hand, you had written, “My brother and my sister,” the verb would be have visited.

In your example, it doesn’t really matter which noun is closer to the verb, because they’re both singular. However, consider the following sentence: Neither the car nor the trucks were able to cross the flooded intersection. Here “car” is singular and “trucks” is plural, but since “trucks” is closer to the verb, we use the plural verb “were.”

Extra Credit:
As I demonstrated above, a compound subject (such as “my brother and my sister”) typically gets a plural verb. Sometimes, though, what looks like a compound subject is actually a simple subject in disguise. This deception occurs with what one grammarian refers to as “clumsy joiners,” phrases such as together with, along with, as well as, and in addition to. Let’s take a look at the example sentence with a clumsy joiner:
My brother, along with my sister, has visited the White House.
Because “along with my sister” is parenthetical, set off from the rest of the sentence, we don’t consider it part of the subject. Therefore, the verb needs to be singular (has) in order to agree with the subject.

I’m glad you asked this question about subject-verb agreement, and I hope you had put your money on “b.”