题目内容：

根据句意和汉语注释，写出单词的正确形式。

1._______ (污染) air does harm to our health. It’s necessary to keep the air fresh and clean.

2.Our success was far _______ (超过) what we thought possible.

3.This kind of disease _______ (传播) so quickly that it drew the government’s attention.

4.The man kept remembering English words every day until he was in his _______ (四十).