1 . 他突然意识到照片中的其他中国人不关心他们的同胞发生了什么事情。（运用it作形式主语）
______________________ the other Chinese men in the photo apparently did not care about what was happening to their fellow countrymen.

3 . 令人惊喜的是，直到20世纪70年代，现代人才有人知道它们。
________________ no one in modern times knew about them until the 1970s.

4 . __________is not unusual to see American university students drive to school every day. (用适当的词填空)

6 . ________ is important to learn English well.

A．This

B．Who

C．It

D．Which

7 . 对于你们这一代青少年来说，喜欢电脑游戏和网络世界并不罕见。
It is __________ for teenagers of your generation __________ computer games and the online world.

8 . _____________________ (很难想象一个没有金属的世界。) Different metals have different uses, for example, steel is used in cars, and iron is used in electrical equipment.

9 . _______ suddenly occurred to him that he had left his keys in the office.

10 . 用新材料来做这些东西要花费大量的能源，因此，只要有可能，就买那些用回收材料制成的物品吧！
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