Which option is grammatically incorrect for the subject "one of the neighbors"?

When determining the grammatical correctness concerning the subject "one of the neighbors," it's essential to understand the agreement between the subject and its verb. In the phrase "one of the neighbors," the subject "one" is singular, which means it requires a singular verb form when making a statement about it.

The phrase "the neighbors has" presents a grammatical error because "neighbors" is plural, and it should be paired with the plural verb "have." Therefore, the phrase should correctly state "the neighbors have."

The correct choice, "the neighbors has," is deemed incorrect due to the mismatch in number between the subject and the verb. A plural subject should always take a plural verb, making this option incorrect in terms of standard English grammar rules.