A、$20. B、$ 10. C、$15. D、$5. B根据对话中女士所说“They are ten dollars each．”可知若男士想买这些样品，每个需付10美元，故本题答案为B。

M: I want to mail these books to New York.
W: By ship or by air, sir?
Q: Where is the man?

M: These cups look nice. How much are they?
W: They are ten dollars each.
Q: How much will the man pay if he buys only one cup?