Subject-verb agreement

EXERCISE:
Choose the correct form of the verb in parentheses in the following sentences.

1. The quality of these recordings (is/are) not very good ...is...
2. The effects of cigarette smoking (have/has) been proven to be extreme harmful ...has...
3. The levels of intoxication (vary/varies) from subject to subject ...vary...
4. Either John or his wife (make/makes) breakfast each morning ...makes...
5. Your glasses (was/were) on the bureau last night ...were...
6. A pack of wild dogs (has/have) fright all the ducks a way ...has...
7. Neither Bill nor Mary (is/are) going to the paly to night ...is...
8. There (was/were) some people at the meeting last night ...were...
9. Neither Jill nor her parents (has/have) seen this movie before ...have...
10. A pair of jeans (was/were) in the washing machine this morning ...was...
11. Advertisements on television (is/are) becoming more competitive than ever before ...are...
12. The crowd at the basketball game (was/were) wild with excitement ...was...