听力原文：W: I've been reading about new healthful food which you can eat in your leisure time and will not put oil weight. It's made from fish. Have you heard anything about it? M: No. I haven't. (19)But I don't like fish very much anyway. W: Don't worry. Although it is made primarily from fish, it actually doesn't have a fishy taste. In fact, it can be flavored with tomato, cheese, or chocolate for instance. M: That sounds good. (20)I suppose this product will be low calorie and high protein, like, eh, health food. W: (20) Yes, you could call it that. And it has a long shelf life, so it won't spoil quickly. It is also easy to digest and can be made from types of fish that usually aren't eaten, or from high-grade fish byproduct. M: Hm… Have you got any samples? I might be willing to try the cheese flavored variety. W: No, none of this seems to be available yet. As I understand it, (21) this fish food probably won't be in the stores for another couple of years, so you have a while to get used to the whole idea. M: A couple of years, huh? It may just take me that long. But thanks for telling me about it. (23)