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

多巴胺舒张肾血管和肠系膜血管的主要机制是

A．促进组胺释放

B．激动β₂受体

C．阻断α₁受体

D．激动多巴胺受体

E．激动M受体