选词填空。

for, by, over, in, from, of, on, with, at

1. I'm sorry           hear that.

2. What's wrong ____ you?

3. I can get some fruit          you.

4. Let's go to see the doctor ____ taxi.

5. Classes are ____.

6. -Is Helen absent? |-No, she's ____.

7. This is the first day ____ the new term.

8. Liu Tao is not          school.

9. We have an English lesson ____ Monday morning.

10. I'm ___   China. I'm Chinese.

将成本划分为（）等，对于分析评价各种不同经营方案，从中选择最优方案，以提高企业物业经营管理服务的经济效益具有十分重要的意义。

A.机会成本

B.目标成本

C.边际成本

D.实际成本

E.差异成本