High school students continue to work hard, _______ they often complain about great burdens and pressures in their life.
| A．as if | B．as long as | C．unless | D．even though |
She felt _____ of having asked such a silly question when the audience couldn't help laughing.
| A．guilty | B．crazy | C．miserable | D．ashamed |
After a short holiday, he _____ himself once more to his studies.
| A．applied | B．converted | C．engaged | D．exerted |
The family is a cooperative enterprise for which it is difficult to _____ rules, because each family needs to work out its own ways to deal with its own problems.
| A．set up | B．put down | C．keep up | D．lay down |
| A．managed | B．succeeded | C．arranged | D．convinced |
Keys should never be hidden around the house since thieves _____ know where to look.
| A．virtually | B．variously | C．unavoidably | D．invariably |