用方框中所给单词的适当形式填空，使对话通顺正确。每词仅用—次(每空—词)。

Clerk: Can I help you?

Mary: Yes, please. I want a pair of  .

Clerk: What  do you like?

Mary; Red,

Clerk: Here you are.

Mary: How  are they?

Clerk: They're twenty .

Mary: OK. Ill  them. Thanks.

Clerk: You're welcome.