
Modern zoos are very different from zoos built fifty years ago. At that time, zoos were places where people could go to see animals from many parts of the world. The animals lived in cages, which were easy to keep clean. However, for the animals, the cages were too small. Although the zoo keepers took good care of them, many of the animals did not feel comfortable, and they often became ill. (以前的动物园,把动物关在笼子里,便于打扫。现在采用开放式饲养方式。)
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