A、$60. B、$50. C、$40. D、$10. C这是一道计算题。根据对话内容，房间原价是50美元，这个月人住可以享受八折优惠，因此房间的实际价格是40美元。注意20％discount的意思是“八折”。

W: Hello, may I help you?
M: Yes, I’d like to book a room for tomorrow.
W: Which kind of room do you prefer, sir?
M:(8) A double room. How much is it?
W:(9)A standard double room is $ 50 per night. But we offer a 20% discount this month.
M: Oh, that’s great. How about the environment?
W:(10)It’s very comfortable, with a view of the sea.
M: OK, I’ll take it. My name is Martin.
W: OK, Mr. Martin. See you tomorrow.
M: Thank you. Bye!
8. Which kind of room does the man want to book?
9. How much is the room?
10. How is the living environment of the room?