21. The company had about 20 notebook computers but only one third _________ used regularly.
Now we have sixty working all day long.
A. is B. are C. was D. wer
22. Not only I but also Brown and Kelly ___________ fond of rock music and computer games.
A. is B. are C. am D. b23. After a knock at the door, the child heard his mother’s voice ____________ him.
A. calling B. called C. being called D. to call
24. A small plane crashed into a hillside five miles east of the city, __________ all four people
on board.
A. killed B. killing C. kills D. to kill
