______ volcanoes for many years, I am still amazed at their beauty as well as th

题型：吉林省期末题难度：来源：

______ volcanoes for many years, I am still amazed at their beauty as well as their potential
to cause great damage.

[ ]

A. Studied
B. Having studied
C. Studying
D. To have been studied

答案

举一反三

__________ for several hours, they came to realize that they had a lot in common.
A. Having chatted
B. chatted
C. To chat
D. Chatting

题型：吉林省期末题难度：| 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：山西省期末题难度：| 查看答案

I"ve earned my own living since I was seven, ______ all kinds of jobs.

[ ]

A. doing
B. having done
C. to do
D. to have done

题型：山东省月考题难度：| 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

_____ to reach them on the phone, we sent an email instead.

[ ]

A. Fail
B. Failed
C. To fail
D. Having failed

题型：同步题难度：| 查看答案