9. They are putting too much carbon dioxide into the atmosphere，which prevents heat from escaping from the earth into space.(P26)

　　翻译句子

　　他们没有阻止他发表自己的观点。

　　_________________________________________________________________

　　Keys: They didn't prevent/stop/keep him from expressing his views.

　　10．How life began on earth is one of the biggest puzzles that scientists found hard to solve.(P27)

　　完成句子

　　①对于下一步该做什么我也不知道。

　　________________as to what to do next.

　　②这是最令人迷惑的问题之一。

　　This is________________problems.

　　Keys:　①I'm puzzled　②one of the most puzzling

What have I learnt in this period?

What am I still confused about?

What should do to make them clear?

Homework课后作业

Finish exercise 3 on P28 and exercise 4 on P63.