12月大学英语四级阅读理解模拟练习（3）

　　Who Knows

　　Since no one knows what scientific discoveries will be made between now and the year A. D. 2000, each of us can make his own predictions.

　　Our prophecies need not be completely wild guesses. We know science has moved forward rapidly in the past 50 years and will continue to do so. If we allow our imaginations to be guided by known research, our prophecies need not be sheer fantasy. We dont have to go so far as to predict that there will be invasion by men from Mars, or that all food and nourishment will be taken in capsule form, or that mechanical men will roam the world.

　　With the scientific information that we have available now, lets make an estimate of progress in air travel. It is likely that within 50 years we shall travel through the air at a speed of 10,000 miles per hour. Too fast? Not at all. Jet-propelled planes can now travel at least 1,000 miles an hour, and jet planes will be outmoded shortly by guided missiles. The X-15 rockets speed in 1961 was 3,690 miles per hour, and scientists are hoping to double and even triple this speed. They will accomplish this speed-up, because there is no apparent scientific obstacle to prevent it.

　　Some day, certain aerodynamic problems will be overcome and missiles will be enlarged to carry at least 25 passengers. When scientists have solved all the problems of constructing and increasing the speed of apparatus-carrying missiles, their skill will lead them to the next stepmissiles for interplanetary flight. This prediction is a scientific possibility in the near future.

　　Flights into outer space began when Sputnik I was launched in 1957, and man first went into space in 1961. During the late 1950s and early 1960s many satellitesman-made astral bodiesorbited the earth and moon. Satellites, which will be controlled by men on earth, may have many beneficial uses. Perhaps scientists will discover a source of energy 100 miles above the earth. This energy could be transmitted to us as a source of power for manufacturing plants or even for our cook stoves. Or one of these missiles might serve as the medium for transmitting communications across the globe. Telephonic

　　communications might be carried on by beaming waves at the missile, which would in turn beam waves at a telephone halfway across the world. The missile might be the telephonic connection, for example, between you in New York, and a friend in Bangkok.

　　Such a satellite might also be used as the transmitting medium for interna-tional television broadcasts. Programs being telecast from a Paris studio could then be seen simultaneously in every other country. This immediate international transmission will surely be a development before the turn of a new century.

　　We may expect to order our clothing, groceries,and other household goods

　　by television-phone. We prophesy that within twenty five years, our telephones will be equipped with television screens so that we can see the person at the other end of the line.

　　Other fields of science have also made gigantic strides in progress. Medicine had operated so efficiently in the past half-century that many diseases have been nearly wiped out. And more will join this disappearing group of diseases. Diabetes and polio are under control. We can hope and expect that cancer will be conquered. Certain skin diseases, like psoriasis and eczema, which are exceedingly common though not fatal, will be eradicated. The victims of annoying diseases will lead pleasanter lives.

　　Even the healthy will benefit from the advances in medicine. Life expectancy already had been lengthened and scientists know that the time is coining rapidly when the person one hundred years old will not be a phenomenon.

　　Even if the birth rate should remain at its present level, the population will be larger as people stay alive longer. Realizing that the increase of population will Strain natural resources, scientists of all kinds are experimenting with methods for extending these resources.

　　One matter of immediate urgency will be our source of food. The larger the population, the greater will be the demand for food. Our arable适合工作的) land is already taxed to capacity. Scientists will have to find a way to mass-produce food by hydroponicsthe science of growing vegetables, or other plants, in wateror by irrigating desert wasteland.

　　This increased demand for food will create an increased demand for water. Certain parts of the United StatesNevada, New Mexico, and Arizona, for examplehave been in desperate need of water for a long time. Periodically, the citizens of New York have been water-rationed because droughts have seriously threatened the water supply in the reservoirs which provide the millions of gallons a day needed in the largest city in the world.

　　Scientists will solve the water problems of the desert and metropolitan areas. Rain-makers will have perfected a simple method, now in the elementary stages of experimentation, for making clouds release their moisture so that the right amount of rain is produced to keep reservoirs at the correct level at all times of the year.

　　Another method of water production will be the purification of salt water taken from oceans. When a simple, cheap method has been worked out for converting seawater into pure water suitable for use in the household and the manufacturing plant, other scientist-engineers will contribute practical mechanical equipment for piping the water from seashore to desert areas.

　　Other improvements of the future will touch our lives more closely. It is possible, for example, to imagine that cities of the future will have underground networks of conveyor belts which would supplement subways and make it possible for people to hop on a rapid conveyor system, sit in a little booth, and shuttle a couple of blocks in safety.

　　Of even more immediate interest than transportation is the clothing of the future. The clothes you will wear at the end of this century may not be of silk, cotton, wool, or even nylon. Clothing will be made of new synthetics and so will the upholstery materials you order by television-phone. To get these synthetic materials, scientists will have devised some electrically controlled apparatus which will allow men to dig twenty miles below the surface of the ground. At that level inside the earth, they may discover many types of rock, now unknown, which will give us these new synthetic materials. Cloth made from these materials will be fire-proof because they come from rock.

　　While these synthetics for cloth are being developed, others will be discovered to take the place of wood and steel. We already have plastic furniture, plastic boats, and plastic dishes. As our wood and steel supplies dwindle ， synthetic materials will be developed for building homes and giant skyscrapers.

　　1. According to the reading selection, the world in the year 2000 will achieve great progress in many fields.

　　2. According to the writer, our predictions about the future should be based on our free imaginations.

　　3. Synthetics in place of silk, cotton and wool will be made from rocks.

　　4. Based on available scientific information, it is predicted in this passage that the speed of air travel 50 years from now will reach 10,000 kilometres an hour.

　　5. Paragraph 8 mainly tells us that many diseases will be cured or under control in the future thanks to the advances in medicine.

　　6. To meet the increasing demand for food, scientists have found a way to mass-produce food by irrigating desert wasteland.

　　7. Underground networks of conveyor belts will be more convenient and more widely used than subways.

　　8. The way to grow vegetables, or other plants, in water is called______.

　　9. The water problems can be solved by producing rain and______.

　　10. One of satellites beneficial uses is to work as the medium for______.