F: Excuse me, sir. I think you drop this on the platform back there. ,M: Oh, thank you so much. It would have been terrible if I had gotten on the subway without my wallet. ,F: Don't mention it. Oh, there's my train. See you.
(A) M: You drop your wallet on the platform. Thank you very much. (B) M: I drop my wallet on the platform. Thank you very much. (C) M: I am really sorry, I did not catch that. Would you slow down, please? (D) M: I drop my subway card on the platform. Thank you very much.
B