题目内容
In nature, genetic diversity is created within certain【C8】______. A rose can be crossed with different kind of rose, but a rose will never cross with a potato. Genetic engineering,【C9】______usually involves taking genes from one species and inserting them into another【C10】______to transfer a desired characteristic. This could mean, for example, selecting a gene which leads to a production of a chemical with anti-freeze【C11】______from an arctic fish, and inserting it into a potato or strawberry to make it frost-resistant.【C12】______, then, biotechnology allows humans to【C13】______the genetic walls that separate species.
Like the green revolution,【C14】______some call the gene revolution contributes to the problem of genetic uniformity--some say even more so【C15】______geneticists can employ techniques such as cloning and【C16】______culture (培养), processes that produce perfectly【C17】______copies. Concerns about the erosion of biodiversity, therefore, remain. Genetically altered plants, however, raise new【C18】______such as the effects that they may have on us and the environment. "We are flying blindly into a new【C19】______of agricultural biotechnology with high hopes, few constraints, and little idea of the potential【C20】______," said science writer Jeremy Rifkin.
【C1】
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【C2】
A．be carried overB．be freed fromC．be held upD．be drawn from
Section B
Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
Researchers disagree whether the "use it or lose it" philosophy holds for cognitive (认知的) aging, but there is some evidence that keeping mentally active can slow age-related declines.
At Pennsylvania State University, Sherry Willis and her husband, K. Warner Schaie, have studied 5,000 people, some since 1956. People lucky enough to avoid chronic diseases may also fare better in intellectual function, they find, perhaps because chronic diseases can restrict lifestyle. and reduce mental stimulation. Similarly, those lucky enough to be relatively affluent also fare better, perhaps because money can buy intellectually stimulating things like travel.
Education helps, too, researchers say, perhaps because it instills the conviction that you can always learn something new. The Schaie-Willis team also has some other observations. Being in a stable marriage with a stimulating spouse, they say, helps maintain intellectual vigor.
Flexibility counts, too. People who stay mentally vibrant are often those who do not insist that "they must do things today as they did before," Schaie says. In neuropsychological (神经心理学的) terms, the ability to see problems in new ways often yields higher scores on tests of mental function. And people satisfied with life also stay more mentally fit, he says.
If you find your mental skills sagging, consider working on specific deficits. When Willis gave 5 hour tutorials (辅导课) on inductive reasoning or spatial (空间的) skills to about 200 people whose skills had declined in the previous 14 years, 40 percent regained lost abilities. That advantage held up seven years later when they were re-tested.
Other ways to stay sharp, Schaie says , are doing jigsaw puzzles to hone (磨炼) visual-spatial skills, working crossword puzzles for verbal skills, playing bridge for memory and simply matching wits at home with players on TV game shows.
Finally, remember this. Even though you may lose some mental skills with normal aging, you also gain in one key area: wisdom. The growth of wisdom loosely defined as the maturation of intellectual abilities that comes with life experience-continue throughout the 40s, 50s, and even 60s.
In this passage, the author mainly discusses ______.
M: Neither could the graduate students.
Q: What can we learn from the conversation？
(17)
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