根据句意，用括号内所给词的适当形式填空。

1. I think everyone has two________(foot).

2. The old man has a serious________(ill).

3. Mr Chen is often________(stress) out.

4. It's easy to stay________(health).

5. My brother's________(speak) Chinese is very good.

直肠脱垂的发病中主要与哪个因素有关：（）

A.风邪

B.热邪

C.燥邪

D.气虚

E.血虚