阅读理解。 Years ago, many zoos kept all kinds of animals in small cages. Small cages made it easy for people to see the animals, but a small cage is not a good place for an animal to live in. Today zoos keep animals in different kinds of cages.The cages are very big and open. They usually have plants and little lake. The cages look like the animals' habits. Zoos help to protect all kinds of animals. They protect animals in the zoo and they protect animals in the wild. How do they do this? Zoos teach people how animals live in the wild. Zoos want people to help protect the animals' wild habitats. Many plants and animals are going extinct (灭绝). Mammoths, which related with the Asian elephants, are now extinct. There are no mammoths in the world today. Scientists say that seventy-four different kinds of living things go extinct every day! Zoos are working together to stop animals from going extinct. 1. Zoos kept animals in small cages so that people can _____. [     ] A. protect them B. see them better C. feed them D. save them 2. Today, zoos keep animals _____. [     ] A. in bigger cages B. in the wild C. in smaller cages D. in the field 3. To protect animals, zoos _____. [     ] A. are trying to keep all kinds of animals B. are trying to free the animals C. teach people more about animals D. want people to feed the animals 4. A mammoth is a kind of _____ that has gone extinct. [     ] A. plant B. bird C. animal D. tree 5. An animal or a plant that is going extinct _____. [     ] A. no longer exists (存在) in the world B. comes into this world soon C. becomes very dangerous D. has fewer and fewer living members