用正确的单词填空。

1. The trees can stop the flood from ______ (wash) the earth away.

2. You'd better ______ (not go) to the supermarket.

3. You must practise ______ (play) the piano every day.

4. He hasn't enough ______ (经验) for the job.

5. He likes to take n            in class.

胃癌患者黑便是由于（）

A.血红蛋白以原形物形式排出

B.血红蛋白中的铁在肠道内被氧化

C.血红蛋白中的铁在肠道内与胃蛋白酶作用

D.血红蛋白中的铁在肠道内与肠液作用

E.血红蛋白中的铁在肠道内与硫化物结合形成硫化亚铁