听力原文：W: David, can I give you a hand with one of those grocery bags? M: Sure, Nancy. Could you take this one, please? I didn't realize how heavy these bags would be. W: Why did you buy so much stuff when you had to walk back home from the store? M: Well, I didn't intend to buy a lot. But I'm having some people over and I guess I needed more than I expected. W: What's the occasion? M: The people I live with, the Smiths, have been on vacation for a month, and I thought I'd surprise them. I'm inviting some of their friends and family for a welcome-home dinner. W: Oh, that's really thoughtful of you. M: I figure it's the least I can do for them. They've been letting me stay with them rent-free when I'm at school. W: Really? That's pretty generous of them. M: Well, they understand how difficult it is to make ends meet when you're a student. They've been such a big help to me. I thought that this might be a small way to thank them for the generosity. (20)