动词专项练习：
1. “I don’t like to travel.” “Have you ever _____ in an airplane?”
a. flying b. flew c. flowed d. flown
2. The center of gravity of the human body ______ behind his joint.
a. located b. locating c. to locate d. is located
3. “Today is very cold, isn’t it?” “Yes, the river is _____ over.”
a. freezed b. freeze c. frozen d. freezing
4. “What happened in that new area?” “New houses ______ recently over there.”
a. are built b. build c. have built d. have been built
5. “When did you go to work?” “As soon as they came, we ______ to work.”
a. went b. were going c. had gone d. go
6. “Did you wait for him very long?” “Yes, I ______ to bed until five in the morning.”
a. did go b. didn’t go c. had gone d. went
7. Perhaps it will be a long time ______ from abroad.
a. when Tom comes back
b. when Tom will come back
c. before Tom comes back
d. that Tom comes back
8. Tom ______ mathematics throughout his college life.
a. bored b. bored with c. was bored d. was bored with
9. ______ that dress when I first saw you at the station?