2. You would be irritated if you watched the mail ________ on your desk every day.
A. putting up   B. to be put up      C. to pile up           D. pile up

3. We shall set Jim ________ the passage.
A. explaining   B. explained        C. to explain          D. explain

4. In fact, she would rather leave for San Francisco ________ in Los Angeles.
A. tostay      B. than stay         C. than staying        D. than have stayed

5. Madame Curies is believed ________ the radium.
A. discovering   B. having discovered   C. to have discovered   D. to discover

（后设答案，大家不要偷看哦~(*^__^*) 嘻嘻……）

KEYS

1. C    2. D    3. C    4. B    5. C