About the scratch on the product, the shop assistant thinks that______.

W: Yes. Can I help you?
M: Yes. You see, I’ve bought this personal stereo at your shop three days ago. And I’m afraid it hasn’t really matched up to what I was told about it.
W: I see. What exactly is the matter?
M: Well, first of all, there’s this large scratch across the front of it.
W: But you should have noticed that when you bought it.
M: But it was in the box, all sealed up.
W: Well, I’m sorry. But it really is your responsibility to check the goods when you buy them. How are we to know that it wasn’t you who made the scratch?
M: That’s ridiculous. But, anyway, it’s not the most important thing. I really am not happy about this other thing.
W: And, what is that?
M: Look, it says here that the noise from it should be undetectable by other people.
W: Yes, that’s right
M: But people can hear it. And it’s really embarrassing on the bus in the underground.
W: Well, I’m sorry. But it must be the way you’re wearing the headphones.
M: Look, I know how to put earphones in my ears. Thank you very much. But what I want to know is what you’re going to do about it at all.
W: Well, I suppose we could exchange it for another model if you really aren’t happy with it.
M: No. I certainly am not.
W: Well, if I just could have the receipt.
M: Ah, yes. Well, there is a slight problem about the receipt.