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: Hi, Mary, you are in Boston, too. I remember you are admitted to Washington University. And are you meeting someone at the airport? ,F: Glad to meet you here, Bob. I am meeting my parents. You are paying a visit to your grandparents? ,M: Right, have you graduated from the university?
(A) F: I'm sorry, I don't understand. Could you say it again? (B) F: Oh, yes. You are seeing parents here? I come to pick my cousins. (C) F: Not yet. I see that your cousins' train has arrived. Go and pick them. (D) F: It's a long journey for your grandparents to take the train to Boston.
A