Task: Dialogue Generation
Input (English): M: The party has begun. Helen hasn't come here yet, did you forget to invite her? ,F: I did invite her yesterday. She planned to come, but she changed her mind this morning. She had to attend a piano class.
(A) M: I’m sorry, I don’t understand. Could you say it again? (B) M: I knew that Helen forgot the party time, so she didn't show up. (C) M: You forgot to invite Helen to the party! (D) M: Fine. So Helen chose to take the piano lesson and refused to come to the party.
Output (English): A