听力原文：W: I don't understand how the inventor earns money from the invention. (19) After all, anyone can copy and sell it. Really, what is a patent? A piece of paper? A philosophy? You can't see it. M: I am glad you asked that. Actually when an inventor has a patent, it's enforceable by the laws in the country where the inventor developed the invention. If anyone makes and sells the product then the inventor can take them to civil court. W: What can the inventor expect to receive if he sues and wins? M: Well, there are different things the court could do, but there's no guarantee. There's a good chance (20) the court could award him compensation and orders to stop the manufacture and sale of goods. It may well be that the goods would be ordered to be destroyed. W: Can the other person being sued do anything to help themselves? M: That's the beauty of the whole thing. Ignorance of the law doesn't count, I'm afraid. However, the other person can counter-sue pretending that they were actually the original inventor. W: You said the inventor is protected by the laws of the country. Is everything equal? Do all countries have the same law? M: No, they're not all equal. You're right. It's only in theory. It is being worked on. The World Trade Organization has developed an agreement, Trade-Related Aspects of Intellectual Property Rights, which makes sure that the patent is valid for 20 years. W: That doesn't make sense. Twenty years is a long time. M: Actually, it does. (21) It's believed that inventors make and sell goods faster after they register the patent because there's a 20-year limitation on the patent. On the other hand, other inventors can use the information the inventor disclosed when the product was registered. Giving the information is all part of the deal. W: Cool. 19. Why can the woman hardly understand that an inventor earns money from the invention? 20.What may the court ask the sued person to do? 21.How does a valid time span of a patent influence the inventor? (1)