Question

In which of the following sentences is there agreement between the subject and the verb?
a. either mavis or cameron is responsible for answering the phone.
b. the number of people who voted were surprisingly low.
c. twenty years are a long time to wait.
d. i think both hard work and time to play is important for each individual

Answer 1

B. The number of people who voted were surprisingly low. 
I believe this is the correct answer.

Answer 2

a. either mavis or cameron is responsible for answering the phone

either is singular