听力原文：W: David, can I give you a hand with one of those grocery bags? M: Sure, Jane. 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: Now the people I live with, the Kremers, have been on vacation for a month and I thought I'd surprise them. I'm inviting some of their friends and families 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. I've been staying with them rent-free while I'm in school. W: Really? That's pretty generous of them. M: Well, they must 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. How does David go back home from the store?