What is at the top of the w_______ food chain?是填world's 还是 whole?why?

What is at the top of the w_______ food chain?是填world's 还是 whole?why?
What is at the top of the w_______ food chain?
附全文：
We sometimes say the lion is "the king of the jungle,(丛林)" because it is stronger and more dangerous than the other animals.It can run faster than most other animals and it can hunt(捕猎) the best.The lion is the highest animal in the land food chain.In the sea,the shark is at the top of the food chain.It can,swim faster than most other sea animals.It can also use its big teeth to catch other sea animals and eat them.
What is at the top of the w_______ food chain?People are!We are not the biggest or fastest,but we are the cleverest.We could not run faster than most animals,so we invented cars and now we can move the fastest.We could not fight better than a lion,so we invented guns.Now we can hunt the best.
People's inventions are clever,but they can be dangerous,too.For example,many years ago in Inner Mongolia,people used guns to kill a lot of wild wolves.The wild wolves usually eat wild rabbits.But in recent(近来的) years,the number of wild rabbits is becoming bigger and bigger because the number of wild wolves is getting smaller and smaller.The wild rabbits competed (竞争) for the grass with the sheep and cows.Much of the grassland became desert because it was seriously destroyed (毁坏) by the rabbits.
Remember that we are a part of the food chain,so we are in danger,too!If we protect animals,we are protecting ourselves.