【答案解析】[听力原文]18-20 M: There'll be a meeting after class. Are you coming, Helen? W: After class? I'm sorry, Mike. I'm afraid I can't. M: But it's quite important. It's about our helping about Bob. W: Oh, I have to go home after class. I'll take care of my mother. She's iii today. M: I'm sorry to hear that. Then we' 11 have the meeting without you. And I'll tell you the meeting tomorrow morning. W: Thanks. I'm really sorry to have to miss the meeting.