A) aceitunas means olives and i know paella has olives in it.
Both of them are correct. You did it right.
I believe the answer you are looking for is "repitieron". Since it is the past tense verb for "they or ellos".
The answer is c. somos.
Since the subject is nosotros, we have to conjugate the verb to make them match. son matches with 'ellas, ellos, or uds.', somos matches with 'nosotros', eres matches with 'tú', and es matches with 'ello, ella, or ud.'
A. Contaban is the correct answer