案例一：
panda is one of the scarcest animals. people in the world like it very much. there used to be many pandas in china long ago. as the balance of nature was destroyed and the weather was getting warmer and warmer, pandas became less. but at present, the number of pandas is increasing year by year. there are now so many pandas that some are being sent to other countries so that people there can enjoy them.
nowadays, the biggest nature park for panda in china is in sichuan. there is a research centre for nature and wild life there. scientists hope that one day they will have enough pandas to be set free and let them live in the wild again.
案例二：
hippopotamus hippopotamus amphibius the hippopotamus is one of the world’s largest and heaviest land animals.it lives partly in water and partly on land.although strictly a plant eater,the hippopotamus has massive jaws with formidable tusks.hippos have
an unpredictable temperament and are capable of biting through small boats and slicing crocodiles in two.hippos trample riverbanks and lakeshores,creating a maze of waterside paths and wallows that they use to get access to the plants they eat.hippos spend their days lazing in or near water,emerging after dark to feed.
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