A、The man’ s girlfriend. B、A salesgirl. C、Customer. D、A passer-by. C女士问“土豆怎么卖?”男士回答“一公斤半个英镑，女士。”由此可以推断出女士是来买菜的顾客，故选C。

W: I told you that you should not be late for class.
M: Well, I’ m sorry. The bus came late and the traffic was heavy.
Q: What might the man be?

W: How much are the potatoes?
M: Half a pound a kilogram, madam.
Q: What’ s the woman?