4. Why did critics think engineered trees dangerous? Because _______. A. these trees can destroy the balance of nature B. everything except trees has been genetically engineered C. trees are home to many endangered species D. these trees may affect normal trees

Passage 55  Cars drive into cleaner future

Ford, the second-largest car maker in the world, celebrates its 100th birthday this month. And it is already looking forward to its next 100 years. Ford expects to have nearly half its cars powered by fuel cells (燃料电池) by the year 2050.    In the meantime, another car maker in the US, General Motors (GM, 通用汽车公司), is building the technology for cars to be powered by fuel cells.  

So, what makes fuel cells so special? Why are car makers so enthusiastic about them?    Fuel cells are based on an electrochemical (电气化学的) process. They change chemical energy from hydrogen and oxygen (氢和氧) into electrical energy.    Fuel cells pollute much less than traditional power sources. They produce little more than water as a by-product. Car makers expect them to cut CO2 emissions (散发) in half and so make cars more environmentally friendly.    Fuel cells are not dependent on oil supplies. Instead, they run on hydrogen, the most common element in the universe. And they can be refuelled. Car makers expect fuel cells to lesson the industry's need to rely on decreasing oil supplies.    Using fuel cells, without the traditional motor, engineers have many more possibilities for developing cars.    A fuel cell frame can last 20 years, so car bodies could change with drivers' needs - or even with the seasons - and be replaced at will. Owners could switch from a sports car to a family car while keeping the same fuel cell frame. This is a much cheaper solution to buying a whole new vehicle.    "A fuel cell car is more than just a new concept car; it's the start of a revolution in how cars are designed, built and used," said GM Chief Executive Rick Wagoner.

While this may sound great, fuel cells are still too expensive to produce. For cars, they can be ten times the price of normal engines. The current test models can cost US$1 million or more.    Besides Ford and GM, a number of other car makers are now testing fuel cell vehicles. And all are aiming for mass production by 2010. By that time, the cost of buying a fuel cell car should be as affordable as that of a traditional car.

3.    Choose the phrase which has the same meaning with “at random”.

A.     at will

B.     on purpose

C.     freely

D.     particularly

Passage 54   America plants tougher trees

Special trees that grow faster, fight pollution, produce better wood, and even sense chemical attacks are being planted by scientists in the US.     When 40 per cent of Hawaii's US$14 million-a-year papaya (木瓜)industry was destroyed by a virus five years ago, work began on creating genetically engineered (转基因的) trees.     Researchers successfully introduced seeds that were designed to resist the virus. Since then, more and more people have been testing genetically engineered trees.    Some researchers put special bacteria into trees to help them grow faster and produce better wood. Others are trying to create trees that can clean polluted soil.    Meanwhile fruit farmers are looking for trees that are strong enough to resist worms, and paper companies want trees that produce more wood and therefore more paper.    The Pentagon (五角大楼,美国国防部所在地) even gave the researchers US$500,000 this year after they developed a pine tree that changes its colours if it senses a chemical attack.    So far, the poplar, eucalyptus (杨树与桉树), apple and coffee trees are among those being engineered. All this is can be done today because we have a better understanding of tree genomes (基因组).    However, some people fear that the genetically engineered trees will cause dangerous results. They are worried that the new trees will breed with natural species and change the balance of the forest environment.

"It could be destructive," said Jim Diamond, an environmentalist. "Trees are what is left of our natural environment and home to many endangered species."    But researchers insist that science could give nature a fighting chance against both natural and man-made dangers.    They hope to answer the critics by stopping the new trees from breeding, so their effect on the environment can be controlled.

4.What is the main purpose of writing this passage?

A.   Expressing the writer’s idea that gene technology will benefit people

B.     Telling people the advantages of gene technology

C.    Telling the readers that gene technology will not benefit people

D.    Explaining that gene technology will also do harm to the humanity

Passage 53 The genetic and environmental influence on man’s intelligence

Although a man may be born clever, his intelligence need also to be further developed. To some extent our intelligence is given us at birth, and no amount of special education can make a genius out of a child born with low intelligence. On the other hand, a child who lives in a boring environment will develop his intelligence less than one who lives in rich and varied surroundings. Thus the limits of a person’s intelligence are fixed at birth, but whether or not he reaches those limits will depend on his environment.

It is easy to show that intelligence is to some extent something we are born with. The closer the blood relationship between two people, the closer they are likely to be in intelligence. Thus if we take two unrelated people at random from the population, it is likely that their degrees of intelligence will be completely different. If on the other hand we take two identical twins will very likely be as intelligent as each other. Relations like brothers and sisters, parents and children, usually have similar intelligence, and this clearly suggests that intelligence depends on birth.

Imagine now that we take two identical twins and put them in different environments. We might send one, for example, to a university and the other to a factory where the work is boring. We would soon find differences in intelligence developing and indicates that environment as well as birth plays a part. This conclusion is also suggested by the fact that people who live in close contact with each other, but who are not related at all, are likely to have similar degrees of intelligence.

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