The ________ expression on her face suggested that she _________ the _________ physics problem.
| A．puzzling；was puzzled by；puzzled |
| B．puzzling；be puzzled over；puzzled |
| C．puzzled；be puzzled by；puzzling |
| D．puzzled；was puzzling over；puzzling |
—How was your trip to Yancheng last week?
—Wonderful! I only felt sorry that I ________ the nature reserve of redcrowned cranes, but the weather was awful.
| A．could visit | B．could have visited |
| C．might visit | D．might have visited |
If I ________ your advice then, I think that the crops could be growing better.
| A．took | B．would have taken |
| C．had taken | D．have taken |
If you ________ home without a word, your parents wouldn't be so worried now.
| A．didn't leave | B．couldn't have left |
| C．hadn't left | D．shouldn't leave |
We ________ here on time but we were caught in a traffic jam.
| A．must have arrived | B．could have arrived |
| C．need have arrived | D．should have arrived |
—Can you keep a secret?
—You ________ worry—I'm not going to mention it to anyone.
| A．needn't | B．couldn't |
| C．mustn't | D．won't |