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”(工业化) 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 (飞行员) 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.
E
A wind tunnel (风洞) is used for teasing planes or plane models. In a wind tunnel air is blown over a plane or a model placed in a test section(区).Wind tunnel test sections are different in size depending on airflow speed requirements. Some low-speed tunnels have test sections large enough for a complete small plane. In the very high speed tunnels used for space testing, however, the model may be as small as a pencil.
There are two ways of feeding air to the test section. In the constant flow tunnel, airflow is produced by electric fans. It is forced through the tunnel to the test section, then through another tunnel section back to the starting point for reuse.
The other way involves (卷入) storing high-pressure air in a box, sending it out by a controlling device(装置) to pass through the tunnel and test section into another box. This way is usually used for a very short period of high-speed airflow.
Wind tunnels are usually used to test planes before they are flown. Problems in a plane can be found when it meets the high-speed airflow in the tunnel. For example, if the wings are built so that they would weaken(become weak) at high speeds, this fact can be discovered in the tunnel, saving many lives and millions of dollars.
In a wind tunnel, scientists also find out how different planes will act different speeds. They find out such things as how the air dives by the wing surfaces, how slowly a plane can fly before it starts to drop, and how fast it can climb.
52.Some wind tunnel sections are larger than others because ________.
A. they are used large planes B. stronger wind can be produced in them
C. they are built to meet a higher speed test D. the wind used in them flows at a lower speed
53.Which of the following shows the right way of feeding air to a wind tunnel section usually
used for a high speed test?
( ← = wind flow = test section)
54. “This fact” in paragraph 4 of the text refers to _______.
A. the wing are not good enough B. it costs a lot to test a plane
C. some problems are found with the plane D. many people will die in a plane accident
55. A wind tunnel can be used to find out ______.
A. how fast a plane can rise B. how smooth a plane’s surface is
C. if a plane can land in a very strong wind D. if a plane will drop when flying at a low height本新闻共 6页,当前在第 4页 1 2 3 4 5 6 |
