Read and choose  阅读理解，在横线上补充正确的句子。

A:   

B: Yes, please. A pair of socks for my son.

A:  

B: Size 6.

A: How about this pair?

B: Are they nice, John?

C:   

B: Are the blue ones all right?

C: Yes, they are.

B:   

A: They are 40 yuan.

B:  ​