The little boy fell asleep while ______TV. So his mother sent him to bed at once.
| A．watched | B．to watch | C．was watching | D．watching |
No student ________ go out of the school campus after 10：00 at night without permission according to the school regulations.
| A．shall | B．must |
| C．should | D．would |
Only after one loses something ________ how precious it is.
| A．he will realize | B．will he realize |
| C．he has realized | D．has he realized |
Life is like riding a bicycle. _____ your balance, you must keep moving.
| A．To keep | B．Keeping |
| C．Being kept | D．Having kept |
Peter, though a green hand, has earned not only the trust of his fellow workers but also ________ of his boss.
| A．one | B．ones |
| C．that | D．those |
A few stars from the entertainment industry, such as Ke Zhendong and Fang zuming, have recently been arrested, which shows that drug taking is becoming _____ increasingly serious threat to society.
| A．the | B．an |
| C．a | D．不填 |