_________the difficult problem,the professor continued to do his experiment.

题型：专项题难度：来源：

_________the difficult problem,the professor continued to do his experiment.     [     ]
A. Having solved
B. Solved
C. Solving
D. Having been sloved

答案

举一反三

Dina,_______ for months to find a job as a waitress,finally took a position at a local advertising agency.   [     ]
A. struggling
B. struggled
C. having struggled
D. to struggle

题型：专项题难度：| 查看答案

_____   to reach them on the phone,we sent an e-mail instead.  [     ]
A. Fail
B. Failed
C. To fail
D. Having failed

题型：同步题难度：| 查看答案

____ in the queue for half an hour, the old man suddenly  realized he had left the cheque in the car.   [     ]
A. Waiting
B. To wait
C. Having waited
D. To have waited

题型：同步题难度：| 查看答案

You can hardly imagine the once clear canal _____ so seriously polluted that no fish can live in it. [     ]
A. have become
B. having become
C. to have become
D. to become

题型：同步题难度：| 查看答案

___ his work, he started to play the computer games.  [     ]
A. Being finished
B. Having finished
C. Finishing
D. Having been finished

题型：同步题难度：| 查看答案