D
　　Our surroundings are being polluted faster than ever and it seems that people cannot prevent it. Time is bringing us more people, and more people will bring us more industry, more cars, larger cities, and the growing use of man-made materials.
　　What can explain and settle this problem? The fact is that pollution is caused by man—by his desire(欲望) for a modern way of life. We make “increasing industrialization”(工業(yè)化) our first aim. So we are often ready to offer everything: clean air, pure water, good food, our health and the future of our children. There is a constant flow of people from the country-side into the cities, eager for the achievements of our modern society. But as our technological achievements have grown in the last twenty years, pollution has become a serious problem.
　　Isn’t it time we stopped to ask ourslves where we are going—and why? It makes one think of the story about the pilot (飛行員) who told his passengers over the loudspeaker : “I’ve some good news and some bad news. The good news is that we ’re making rapid progress at 530 miles per hour. The bad news is that we are lost and don’t know where we’re going.” The sad fact is that this becomes a true story when speaking of our modern society.
48. Man cannot prevent the world from being polluted because _______.
A. the population of the world is increasing faster
B. people use too many man-made materials
C. we have more industry 　　　 D. we are producing more cars, trucks and buses
49. According to the passage, what does man care most among the following?
A. Health.　　B. Industry.　　C. Clean air　 D. The future of the children
50.The story about the pilot tells us that _______.
A. man knows where the society is going
B. people don’t welcome the rapid development of modern society
C. man can do little about the problem of pollution
D. the speaker is worried about the future of our society
51.What dose the writer really want to say in the passage?
A. With the development of technology, pollution has become a serious problem.
B. We should control the speed of the development to stop pollution.
C. It’s time we did something to reduce pollution.
D. As industry is growing fast, pollution is the natural result.