Given the task definition and input, reply with output. In this task you are given a small conversation between two persons and 4 options on how the conversation should continue. Your job is to choose the most reasonable option. The conversation and the options are separated by a newline character. Each dialogue in the conversation are separated by a comma. F and M indicate female and male, respectively.

M: I need to use the restroom, but the door is locked. No one is in there because I already knocked on the door. Can you give me the key? ,F: Well, the restroom is for customers only. You'll need to buy something before I can give it to you.
(A) M: You mean I need to look for the keys by myself? (B) M: Excuse me, could you repeat the question? (C) M: You mean I need to buy something before using the restroom? (D) M: You mean I need to wait the staff only toilet for a while?
C