根据语法和文章的上下文意思填入所缺单词。

    Animals are  (people) friends. But many wild animals are (face) the danger of(die) out. There're many reasons. First, their living environment change a lot because of the (develop) of many cities. Also, (pollute) becomes worse and this make wild animals lose homes. Second, some people are killing animals getting their fur, skin, teeth and meat.

    People should do something to help protect (endanger) wild animals. For example, people can build some nature reserves to save wild animals' homes. Animals can live (free) there. Besides, people are not allowed kill wild animals. If we start protecting our animal friends, our world will become much better.