从A、B、C、D四个选项中，选出可以填入空白处的最佳选项。

1. It was been 　　　　　to our attention that global warming is becoming more and more serious and we have to take measures to protect the earth.

A. taken　　　　　 B. caused

C. brought　　　　 D. attracted

5. As time passed by, people begin to realize the importance of not having too many children.

　　　 　time 　　　　, people begin to realize the importance of not having too many children.

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4. To talk with your mouth full is bad manners.

　　　　　　　　 　　　　　　　　　bad manners to talk with your mouth full.

3. We haven’t heard from her for seven years.

It is seven years 　　　　　we last heard from her.

It is for seven years 　　　　we haven’t heard from her.

2. Since you have understood it so well, there is no need to explain it again.

Since you have understood it so well, 　　　　　is not 　　　　to explain it again.

1. How old is the man who is standing by the gate?

How old is the man 　　　　　　　　　the gate？

5. As the boy 　　　　　(play) the drums, he　　　 　(begin) to feel sick.

4. By the time we 　　　　　(get) back, he 　　(complete) the oil painting.

3. While Zhao Jie 　　　　(watch) a quick show, his parents came in.

2. I want to go to the cinema tomorrow.　 I think I 　　　　　(ask) Li Kang to come with me.