根据短文内容选择可以填入空白处的最佳答案。(Choose the best answers to complete the passage．)

　　We sometimes call the lion“the king of the jungle(丛林)”because it is stronger and more dangerous than other animals．It can 　　1　　 faster than many animals and it can hunt(捕猎)the beast．It is the highest animal in the 　　2　　 food chain(食物链)．

　　In the sea, the shark is one of the animals at the 　　3　　 of the food chain．It can swim faster than 　　4　　 other sea animals, and it can use its big teeth to eat them．

　　What is at the top of the world's food chain?　　5　　 are! We are not the biggest or fastest, but we are the 　　6　　．We could not run faster than cheetahs(猎豹), so we 　　7　　 cars and now we can move the fastest．We could not 　　8　　 better than lions, so we invented guns(枪)．Now we can hunt the beast．

　　People's inventions are clever, but they can be 　　9　　, too．For example, people invented 　　10　　, and now they make the air and rivers dirty．This can make 　　11　　 changes．Dirty rivers kill fish．　　12　　 bears cannot eat the fish and the bears die．If we kill one part of the food chain, 　　13　　 also die．Remember that we are a part of the food chain, 　　14　　 we are in danger too! If we protect animals, we are protecting 　　15　　!We should and we could do something for the world!

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