______ it is true that a student's most important goal is to do well in his or her studies, it doesn't need to be the only goal.
| A．When | B．As |
| C．While | D．Before |
—Did you find the missing couple in the mountain yesterday?
—No, but we ________ to get in touch with them ever since.
| A．have tried | B．have been trying |
| C．had tried | D．had been trying |
—Such a mistake could have been avoided.
—Unfortunately, he _______ the mistake again and again.
| A．repeated | B．would repeat |
| C．had repeated | D．would have repeated |
—May I remind you that a Mr. Wang is waiting outside, sir?
—Oh, that’s right. I about it.
| A．forget | B．had forgotten | C．forgot | D．have forgotten |
—Did you enjoy your holiday?
—Yes, it’s the best holiday I these years.
| A．had | B．have had | C．had had | D．would have |
Just look at the room. My roommate ____ up his clothes.
| A．is never hanging | B．will never hang | C．never hangs | D．never hanged |