根据首字母及汉语提示，完成下列单词的拼写，使句意明确，语言通顺。

1. It is i_________ (重要的) for you to keep healthy.

2. He r_________ (收到了) a story-book on his last birthday.

3. We shouldn't throw rubbish e_________ (到处) to protect environment.

4. A_______ (四月) is the fourth month of a year.

5. "Help y_________ (自便) to some fish." Mum said to my friends.

激素避孕的作用机制包括（）。

A.阻止精子进入 * *

B.抑制排卵

C.改变宫颈黏液性状

D.改变子宫内膜形态与功能

E.改变输卵管功能