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 ______ faster than other sea animals. They have wide mouths and sharp (锋利的) ______. 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 ______. We can’t run fast, but we ______ cars; We can’t fight better, but we invented guns (枪),… Many inventions are useful to us. ______, they’re also harmful. People ask the ______ 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 danger of ______ out…

Don’t forget that we’re part of the food chain. We should leave enough ______ for animals to live in. We should do something to stop people from ______ animals. We must know that protecting animals is just to protect ______.