"Yes, I did. I heard him ______ three times."
A. knocking B. knocked C. being knocking D. knock
12.Peter, John and Tom each ______.
A. say they came first B. says they came first C. says he came first D. say came first
13.Through long power lines electricity goes ______.
A. to the place needed B. there it is needed C. where it is needed D. which it is needed
14. ______from the apple tree.
A. It down fell B. there it is needed C. Down fell it D. Fell it down
15.The service in this restaurant is very poor; there are not enough waiters to wait ______ customers.
A. on B. for C. with D. to