A
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 a little lake. The cages look like the animals' habitats (栖息地)．
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. Mammoths, which are related with Asia elephants, are now extinct. There are no mammoths in the world today. Scientists say that seventyfour different kinds of living things go extinct every day!
Zoos are working together to stop animals from going extinct.
21．Zoos kept animals in small cages so that people can ________.
A．protect them B．see them better
C．feed them D．save them
22．Today, zoos keep animals ________.
A．in bigger cages B．in the wild
C．in smaller cages D．in the field
23．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
