用所给词的适当形式填空。

1. — Where is Mr. Wang?

    — He ______ (go) to the library. He wants to borrow some library books.

2. At first she ______ (think) about going camping, but later she changed her mind.

3. They are from ______ (foreigner) countries.

4. I ______ (discover) the truth, but I couldn't tell it to others.

5. How long have you been ______ (wait) here?

变构剂调节的机理是( )。

A．与活性中心结合

B．与辅助因子结合

C．与必需基团结合

D．与调节亚基或调节部位结合

E．与活性中心内的催化部位结合