You turn off the lights when you leave the classroom.

I to bed I finished my homework.

A: Where have you been, Li Hai? I called you, but you weren't in.

B:

A:

B: I found that the factory was pouring waste water into the river near it. Lots of fish have died.

A:

B: Do you think "Greener China" can do something?

A:  if they know about this thing, they will prevent it. Let's write to them at once.

B:  I think everything will become better.

— For about two years so far.

Our living environment is being polluted faster than before and it seems nobody can prevent it. Time brings us more people, and more people bring us more industry, more cars, larger cities and growing use of man-made materials.

How can we understand and solve this problem? The fact is that pollution is caused by man —by his desire (欲望）for a modem way of life. So we are often ready to offer everything: clean water, good food, our health and the future of our children. There are more people from the countryside moving into the cities and enjoying the modem society. But as the technological momentum (势头) has grown in the last twenty years, pollution has become a serious problem.

Now we have to stop to ask ourselves where we are going and why. It makes one think of the story about the airline pilot who told his passengers over the loudspeaker, "I've got some good news and bad news. The good news is that we're going at 530 miles per hour. The bad news is that we're lost and don't know where we are going." The sad fact is that this problem becomes a true story when speaking of our modem society.