In the past hundred years, there have been violent natural disasters occurring worldwide, such as     1    （洪水）,     2    （干旱），mudslides and     3    （地震）. The disasters have caused millions upon millions of people deaths,     4    （毁坏）countless homes, and wiped out numerous pieces of fertile land.

Now more and more people become aware that what we have done have done damage to the earth. So it is     5    （紧急的）for us to stop damaging it, and to do our best to     6    （保护）it, for we have nowhere to go and survive except where we are now.