选择方框内所给的单词并用适当形式填空。 Stop  live  scientist  protect  animal  kind  difference  open  easy  wild Years ago, many zoos kept all 1______ of animals in small cages. Small cages made it 2______ for people to see animals, but a small cage isn't a good place for an animal to live in. Today, zoos keep animals in 3______ kinds of cages. The cages are very big and 4______. The cages look like the 5______ habitats. Zoos help to protect animals, They protect animals in the zoo and they protect animals in the 6______. How do they do this? Zoos teach people how animals live in the wild. Zoos want people to help 7______ the 'wild habitats'. Many plants and animals are going extinct. 8______ say that seventy-four kinds of 9______ things go extinct every day! Zoos are working together to 10______ animals from going extinct.