二. 单项选择 （共15小题，每题1分，满分15分）
6. I ordered him not to be late, so he _______his clock.
A. put back B. put off C. put forward D. put away
7. ________do you base your calculation?
A. On which B. On what C. About what D. For what
8. It’s dangerous to get close to the building___________.
A. under construction B. built C. been built D. building
