Only when something gets lost _____________.
| A．can you realize how important it is to you |
| B．how important you can realize it is to you |
| C．you can realize how important it is to you |
| D．can you realize how important is it to you |
_________ she would have avoided the accident.
| A．She was more careful | B．If she was more careful |
| C．Had she been more careful | D．She had been more careful |
Seldom _________ any mistakes during my past five years of teaching in this university.
| A．would I make | B．I did make |
| C．should I make | D．did I make |
It was _________ he said _________ disappointed me at that time.
| A．what; that | B．that; that |
| C．what; what | D．that ； what |
It was only when I reread his poems recently _________ I began to appreciate their beauty.
| A．until | B．that |
| C．then | D．So |
Hardly _________ the house when he was caught.
| A．the thief had entered | B．entered the thief |
| C．had the thief entered | D．was the thief entering |