选择适当的句子补全对话。

A. So I'm often late  for school.    

B. Usually by bus

C. I leave home at about 7: 40.      

D. Why not 

E. What time do you usually get up?  

F. Don't worry

Teacher: How do you usually come to school?

Student: 1._________

Teacher:2._________

Student: I usually get up at 6:40.

Teacher: Well.  What time do you usually leave home?

Student: 3._________Teacher: Why not come a little earlier?

Student: Sorry,  I can't.

Teacher: 4._________Student:  My mother is ill in bed.  So I have to look after her and give

              her medicine at the right time.5. _________

Teacher: I know.  You're a good boy!

从经济学的一般意义上讲，成本是商品经济的价值范畴，是商品（）的组成部分。

A.价值

B.价格

C.销售

D.流通