M: What is a reasonable tip to leave to the waitress? ,F: It's up to you. I usually leave 20% of the dinner price.
(A) M: Do you know how to reduce the price? (B) M: I’m sorry, I didn’t understand. Could you repeat a little louder, please? (C) M: Why do you think the reasonable tip leaving to the waitress is 20% of the dinner price? (D) M: Do you know how to order a dinner?
C