请通读下面对话，根据对话内容，从方框内的选项中选出能填入空白处的最佳选项，选项中有一项为多余选项。

A. Why? B. Can I take it for eighteen yuan? C. Here is a purple bag. D. I want to buy a bag. E. What about this? F. For your parents?

W: Can I help you, boy?

M: Yes, please.

W: Who do you buy it for?

M: No, for Miss Smith.

W:

M: Because she is my favorite teacher and next Friday is her birthday.

W: Oh, I see. And it's twenty yuan.

M: OK. The bag looks nice. But I only have eighteen yuan.

W: OK. Here you are.