根据句意及首字母提示完成单词。

1. Drinking milk every day is good for our h_____.

2. A lot of v_____ make us keep in good health.

3. On Valentine's Day (情人节) boys often send c_____ to their girlfriends.

4. J_____ food is not good for one's health.

5. —What do you think is the most difficult s_____?

   —I think it's math.

6. My healthy lifestyle helps me get good g_____.

7. There are a lot of animals in the z_____.

冷水机组使用的工质大部分是（）。

A.R22

B.R717

C.R12

D.R744