用括号中所给词的适当形式填空。

1. You should be much               . It's good for your health. (health)

2. Recently I listened a song               Heart Strings. (call)

3. He told me that he               in that school for 10 years. (teach)

4. I've been (try)               to cheer him up for 20 minutes.

5. The telephone               (invent) before the car.

因为安全原因，在何种功率状态下，才可以通过安全通道接近发动机（）

A.关车后

B.慢车时

C.部份功率时

D.大功率时