名句默写。

热机的广泛使用已成为一个国家工业化程度的标志，人类的现代生活已越来越离不开各种热机，热机从根本上改变着我们的世界。下列相关说法正确的是（）

Protect Wild Animals

    Animals are our good friends．We live in the same Earth．Animals and people can't  be separated from each other．But some animals are getting less and less．So it's important to us to protect animals，especially wild animals．Some people kill wild animals because of money．It's wrong．Now people need more places to live in．We explore the forest．  Animals have less places to live in．The number of wild animals decreases year by year．So we should protect wild animals．

生物进化的内在因素是（    ）