听力原文：W: Professor, (19)I'm going to take part in a debate on advertising tomorrow. Would you please give me some hint? M: That's interesting. I should like to hear what young people think about advertising. W: Well, (20)we wouldn't know what there was to buy if we didn't have advertisements. M. Yes. that's true up to El point. Advertisements provide information that we need. If someone has produced a new article, naturally the seller wants to tell us about it. W: Yes, and (20) advertisements tell us which product is the best. M: Do they? I don't think so. Every manufacturer says that his product is the best, or at least tries to give that impression. Only one can be the best, so the others are misleading us, aren't they? W: Well, in a way, I suppose, but we don't have to believe them, do we? M: Are you saying that advertisements aren't effective? (21)I don't think that intelligent businessmen would spend millions of dollars on advertising if nobody believed the advertisements, do you? W: (20)Perhaps not, }0ut after all, it's their money that they're spending. M: Is it? I think not. The cost of advertising is added to the price of the article. You and I and all the other people who buy the article pay for the advertising! W: Well, (20)I suppose we get something for our money--some information. M: Yes, but don't forget it's often misleading information, and sometimes harmful. (20)