Select the grammatically correct choice:

1. Either Alvin, Simon or Theodore are going to sing at the party.
2. Either Alvin, Simon or Theodore is going to sing at the party.

2. Either Alvin, Simon, or Theodore is going to sing at the party.

The grammatically correct choice is:

2. Either Alvin, Simon or Theodore is going to sing at the party.

The grammatically correct choice is:

2. Either Alvin, Simon or Theodore is going to sing at the party.

To determine the correct answer, we need to consider subject-verb agreement. In this sentence, the subject is "Either Alvin, Simon or Theodore." When "either" is used as a subject, it is considered singular. Therefore, it requires a singular verb form, which in this case is "is."