We often say that lions and tigers are kings of animals. They ’ re the best hunters ( 猎手 ) and they ’ re at the top ( 顶端 ) of the food chain ( 链 ) on land. But the best hunters in the sea are sharks. Sharks are bigger and swim 1 faster than other sea animals. They have wide mouths and sharp ( 锋利的 ) 2 . They are at the top of the sea food chain. What ’ s at the top of the world ’ s food chain? Human beings ( 人类 )! We ’ re not strong, but we ’ re the 3 . We can ’ t run fast, but we 4 cars; We can ’ t fight better, but we invented guns ( 枪 ), ... Many inventions are useful to us. 5 , they ’ re also harmful. People ask the 6 for too much. For example, we ask for food, wood, fur and so on. As a result, forests are becoming smaller and smaller. Rivers are dirty and some animals are in er of 7 out ... Don ’ t forget that we ’ re part of the food chain. We should leave enough 8 for animals to live in. We should do something to stop people from 9 animals. We must know that protecting animals is just to protect 10 .