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Questions 21 to 25 are based on the following passage.
Many Americans harbour a grossly distorted and exaggerated view of most of the risks surrounding food. Fergus Clydesdale, head of the department of food science and nutrition at the University of Massachusetts-Amherst, says bluntly that if the dangers from bacterially contaminated chicken were as great as some people believe, “the streets would be littered with people lying here and there.”
Though the public increasingly demands no-risk food, there is no such thing. Bruce Ames, chairman of the biochemistry department at the University of California, Berkeley, points out that up to 10% of a plant’s weight is made up of natural pesticides (杀虫剂). Says he: “Since plants do not have jaws or teeth to protect themselves, they employ chemical warfare.” And many naturally produced chemicals, though occurring in tiny amounts, prove in laboratory tests to be strong carcinogens-a substance which can cause cancer. Mushrooms (磨菇) might be banned if they were judged by the same standards that apply to food additives (添加剂). Declares Christina Stark, a nutritionist at Cornell University: “We’ve got fat worse natural chemicals in the food supply than anything man-made.”
Yet the issues are not that simple. While Americans have no reason to be terrified to sit down at the dinner table, they have every reason to demand significant improvements in food and water safety. They unconsciously and unwillingly take in too much of too many dangerous chemicals. If food already contains natural carcinogens, it does not make much sense to add dozens of new man-made ones. Though most people will withstand the small amounts of contaminants generally found in food and water, at least a few individuals will probably get cancer one day be cause of what they eat and drink.
To make good food and water supplies even better, the Government needs to tighten its regulatory standards, stiffen its inspection program and strengthen its enforcement policies. The food industry should modify some long-accepted practices or turn to less hazardous alternatives. Perhaps most important, consumers will have to do a better job of learning how to handle and cook food properly. The problems that need to be tackled exist all along the food-supply chain, from fields to processing plants to kitchens.
21. What does the author think of the Americans’ view of their food?
A) They overstate the government’s interference with the food industry.
B) They are overoptimistic about the safety of their food.
C) They overestimate the hazards of their food.
D) They overlook the risks of the food they eat.
22. The author considers it impossible to obtain no-risk food because ________.
A) no food is free from pollution in the environment
B) pesticides are widely used in agriculture
C) many vegetables contain dangerous natural chemicals
D) almost all foods have additives
23. By saying “they employ chemical warfare” (Line 4, Para. 2), Bruce Ames means “________”.
A) plants produce certain chemicals to combat pests and diseases
B) plants absorb useful chemicals to promote their growth
C) farmers use man-made chemicals to dissolve the natural chemicals in plants
D) farmers use chemicals to protect plants against pests and diseases
24. The reduction of the possible hazards in food ultimately depends on ________.
A) the government
B) the consumer
C) the processor
D) the grower
25. What is the message the author wants to convey in the passage?
A) Eating and drinking have become more hazardous than before.
B) Immediate measures must be taken to improve food production and processing.
C) Health food is not a dream in modern society.
D) There is reason for caution but no cause for alarm with regard to food consumption.
Questions 26 to 30 are based on the following passage.
There are some each phenomena you can count on, but the magnetic field, someday is not of them. It fluctuates in strength, drifts from its axis, and every few 100,000 years undergo, dramatic polarity reversal-a period when North Pole becomes South Pole and South Pole becomes North Pole. But how is the field generated, and why is it so unstable?
Groundbreaking research by two French geophysicists promises to shed some light on the mystery. Using 80 metres of deep sea sediment (沉淀物) core, they have obtained measurements lots of magnetic-field intensity that span 11 polarity reversals and four million years. The analysis reveals that intensity appears to fluctuate with a clear, well-defined rhythm. Although the strength of the magnetic field varies irregularly during the short term, there seems to be an inevitable long-term decline preceding each polarity reversal. When the poles flip—a process that takes several hundred thousand years-the magnetic field rapidly regains its strength and the cycle is repeated.
The results have caused a stir among geophysicists. The magnetic field is thought to originate from molten (熔化的) iron in the outer core, 3,000 kilometers beneath the earth’s surface. By studying mineral grains found in material ranging from rocks to clay articles, previous researchers have already been able to identify reversals dating back 170 million years, including the most recent switch 730,000 years ago. How and why they occur, however, has been widely debated. Several theories link polarity flips to external disasters such as meteor (陨星) impacts. But Peter Olson, a geophysicist at the Johns Hopkins University in Baltimore, says this is unlikely if the French researchers are right. In fact, Olson says intensity that predictably declines from one reversal to the next contradicts 90 percent of the models currently under study. If the results prove to be valid geophysicists will have a new theory to guide them in their quest to understand the earth’s inner physics. It certainly points the direction for future research.
26. Which of the following titles is most appropriate to the passage?
A) Polarity Reversal: A Fantastic Phenomenon of Nature.
B) Measurement of the Earth’s Magnetic-Field Intensity.
C) Formation of the Two Poles of the Earth.
D) A New Approach to the Study or Geophysics.
27. The word “flip” (Line 6, Para. 2) most probably means “________”.
A) decline
B) intensify
C) fluctuate
D) reverse
28. What have the two French geophysicists discovered in their research?
A) Some regularity in the changes of the earth’s magnetic field.
B) Some causes of the fluctuation of the earth’s magnetic field.
C) The origin of the earth’s magnetic field.
D) The frequency of polarity reversals.
29. The French geophysicists’ study is different from currently prevailing theories in ________.
A) its identification of the origin of the earth’s magnetic field
B) the way the earth’s magnetic intensity is measured
C) its explanation of the shift in the earth’s polarity
D) the way the earth’s fluctuation rhythm is defined
30. In Peter Oslo’s opinion the French experiment ________.
A) is likely to direct further research in the inner physics of the earth
B) has successfully solved the mystery of polarity reversals
C) is certain to help predict external disasters
D) has caused great confusion among the world’s geophysicists
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