用括号中所给词的适当形式填空（5分）
76.  You should be much __        __.  It's good for your health.  (health)
77.  Recently I listened a song ___       _ Heart Strings.  (call)
78.  He told me that he __       _ in that school for 10 years.  (teach)
79.  I've been __        __ (try) to cheer him up for 20 minutes. 
80.  The telephone __         _ (invent) before the car. 

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.