And the other vaulters have been training for months.
which case type pronoun is required to complete the sentence?
a. nominative
b. possessive
c. objective
d. antecedent

The case type pronoun that is required to complete the sentence would be A) nominative. It is the subject case, and since we need a subject here, nominative is the option we have to use. For example:
They and the other vaulters have been training for months.
They is a nominative personal pronoun.
Possessive would be theirs, and as you can see, it doesn't fit.
Objective would be them, and it is also incorrect.
Antecedent just means a pronoun.

The answer is a i think good luck