Which sentence contains an error in subject-verb agreement?
a. macaroni and cheese is being served in the cafeteria today.
b. many citizens of clarkson county are fighting to save the local wetlands.
c. each of the athletes have trained hard for the competition.
d. my mother or my father is going to pick me up from swim practice.

The answer to your question would be that the sentence that contains an error in subject-verb agreement is the following one: My mother or my father is going to pick me up from swim practice. That is, the correct option would be D.

Subject-verb agreement refers to the fact that the subject and the verb must agree with one another in number (singular or plural). Consequently, if the subject is singular, its verb must also be singular; if a subject is plural, its verb must also be plural. In this case, the subject is plural since it refers to two people (mother and father), so the verb must also be plural.