听力原文：M: Hi, Claire. How does it feel to be back on campus? W: Gee, Hi, well, to tell you the truth, I have mixed feelings. M: Oh, why? W: I have this great summer job that I really hated to leave. I worked at the wild life research center in Maryland. M: That makes sense for a genetic major. What did you do? Clean the cages? W: This is a wild life center, not a zoo. This place breeds endangered species and tries to prepare them for life in the wild. M: You mean the endangered species like the tiger and the panda? W: Well, endangered species, yes. But not tigers or pandas. I work with whooping cranes and sandhill cranes. I taught the baby crane how to eat and drink, and I help the vets to give medical check-ups. M: I can see it was hard to leave that job. But how did you teach a bird how to eat and drink? W: We covered ourselves up with cloth and used puppets made out of stuffed cranes to show the baby chicks what to do. Then the chicks copied what the puppets did. M: Cloth? Puppets? Sounds like fun. W: It was. The cloth and puppets are the key tools. We all covered ourselves up, the scientists, the vets, the junior staff, everybody. You see, baby cranes will become attached to their caretakers. M: So if the caretaker is a person, the crane will stay in places where people are. W: Yeah. And their chances for survival aren't very good. But by covering ourselves and using cloth and puppets the chicks are more likely to seek out other birds rather than people. And their transition to the wild has a better chance of being successful. M: A chance of being successful? Hasn't this been done before? W: It's been done with sandhill cranes and everyone is optimistic about its work with whooping cranes too. M: If this works, it should increase the number of cranes in the wild. W: Yeah. It's exciting, isn't it? Why dues the woman say she has mixed feeling?