选择合适的句子补全对话。

A：

B：Yes, please. I want a sweater.

A：                      

B：Black.                                 

A：Sorry, we don't have any black sweaters. Look at these sweaters. They are very nice. 

B：                            

A：35 dollars.

B：OK, I'll take it.

A： .

B：Thank you.

A：.

A.What colour do you want?

B.Here you are.

C.Can I help you?

D.You're welcome.

E.How much is this one?