Which verb agrees in number with its subject? either my cousins or my sister out at the fair today. a. is b. are c. were d. have been

The best answer for this question would be:

C. were helping

The answer is C, because the one noun is a singular while the other one is paired with a plural, so the verb should be in plural form as much as possible.

i think it could possibly be b

i believe the answer is b. we