30. throw away 扔掉；throw about 四处乱扔

29．be careful with 细心；认真 be careful of/about 注意；留意

28. in the wild 处于野生状态

INTEGRATING SKILLS

27. set…free 释放 =free

26. explain sth to sb 向某人解释…=explain to sb sth

25. at present 目前 at the present time 　　be present at 出席

24. devote oneself to sth/doing sth 致力于… be devoted to sth/doing sth 投身于 a devoted friend / wife

23.If we know more about what causes endangerment, we may be able to take measures before it is too late. 如果我们能更多地了解致使生物濒危的原因，就能及时采取补救措施。

They are thinking of buying the house before the prices go up. 他们正在考虑趁房价未涨时把房子买下来。

If you don’t like the present job, I suggest you look for another one before it is too late. 如果你不喜欢目前的工作，我建议你趁早另谋出路。

He hung up before I could say a word. 　我还没说一句话，他就挂了电话。

LANGUAGE STUDY

22. make a big difference 大改观；影响大

21. first of all 首先 at first; above all