1 . Some people think ______ necessary to explore the oceans because of the potential amounts of resources. (用适当的词填空)

2 . She finds ___________ challenging to balance her social life with her study. (用适当的词填空)

3 . ______is widely acknowledged that computers have become a vital part of our society.

A．As

B．It

C．What

D．Which

4 . Communicating through a screen makes ____________ more difficult for children to concentrate. （用适当的词填空）

5 . Some people consider _______ a waste of time surfing the Internet, while others hold different opinions. (用适当的词填空)

6 . It is not unusual for teenagers of your generation ________ to computer games and the online world.

A．to be attracted

B．attracted

C．being attracted

D．to attract

7 . ________ is urged that the public should promote their awareness to protect the rare animal. (用适当的词填空)

8 . I like ______ in the autumn when the weather is clear and bright.

A．this

B．it

C．that

D．what

9 . 门咔嚓一声锁上时，他突然想到自己把钥匙忘在了里面。
________________ he had left his keys inside just as the door clicked shut.