阅读理解。

     It's seven thirty now. It's time to go to school. Our classroom is behind the trees.It's very nice. There

is a map of China on the wall. Twenty boys and fifteen girls are in the classroom. There are some flowers

on the teacher's desk. They are for our teachers. We have four classes in the morning and two in the

afternoon. We aren't at school on Sunday.

1. The students go to school at_____.

A. 7:13

B. 7:03

C. 7:30

2.Their classroom is_____some  trees.

A. behind

B. in

C. under

3. A map of China is on the_____.

A. desk

B. wall

C. blackboard

4. The_____are for the teachers.

A. maps

B. desks

C. flowers

5. There are_____students in this class.

A. forty-five

B. fifteen  

C. thirty-five

能帮助新生多肽链正确折叠的物质是（）。

A.分子伴侣

B.别构剂

C.变性剂

D.配体

E.辅基