四六级考试

【单选题】
A、Mystery in the LunchboxHungry Sit down. We’’re having catfish, corn on the cob, baked potatoes and fresh tomatoes. This might turn out to be the most nutritious meal of your life. It might even be the best-tasting dinner you ever haD、On the other hand, it might induce an allergic (过敏性的) reaction — even though you are not allergic to any of these foods.Different Opinions aboutBiotechnology (生物工程) ProductsLast week’’s announcement that the U.S. federal government would impose no special regulations on bioengineered foods, in effect permitting them to be marketed exactly like nature’’s own, proclaims a potentially vast change in our food supply. "We will not compromise safety one bit," Vice PresidentDan Quayle told the press. "And consumers will enjoy better, healthier food products at lower prices." Many specialists in biotechnology agree — in fact, they see consumers around the world benefiting from a new, genetically-engineered green revolution — but critics are urging the government to move ahead more cautiously. "We should have learned from the history of regulating pesticides (杀虫剂) that we never knew the long-term consequences until it was too late," saysEllen Haas, executive director of Public Voice for Food and Healthy Policy, a WashingtonD、
C、-based advocacy group. The Food andDrugAdministration maintains that most bioengineered foods present no special safety issues. "We’’re saying this is just another plant-breeding technique," saysEric Flamm, deputy director of the FDA’’s Office ofBiotechnology. HowDoes Recombination ofDN
A、Work Here’’s how bioengineering works: all cells containDNA, the long molecule (分子) shaped like a double helix (螺旋).
A、gene is a swatch (样本) ofDN
A、that controls a certain characteristic of the organism. In the 1970s scientists discovered they could clip off a gene-length swatch from aDN
A、molecule, and later they learned to affix (固定) it to a differentDN
A、molecule — a cut-and-paste job that became known as gene splicing and results in what’’s called recombinantDN
A、Immediately, visions of carrots with the flavor of peanut butter began dancing in the imaginations of scientists and food writers alike.But most current experiments are less exotic (异乎寻常的). In many ways the new technology differs little from traditional crossbreeding. One Product ofBioengineered TechnologyThe first example of recombinantDN
A、in a form suitable for lunch makes its debut (首次露面) next summer: the Flavr Savr tomato. Scientists atCalgene, In
C、, a biotech company based inDavis,California, isolated the gene in the tomato that triggers the enzyme (酶) responsible for rotting and rendered it inactive. Rather man having to be picked hard and green for easy shipping, the tomatoes stay on the vine about five days longer than usual. They can be shipped* without refrigeration, which also helps retain flavor, and they’’ll resist rotting for more man three weeks, twice as long as their conventionally grown cousins. They aren’’t perfect: like other supermarket tomatoes they’’re grown with pesticides, they may be waxed, and they still lack the last three to five days of vine-ripening that homegrown tomatoes enjoy. Sampled atCalgene’’s headquarters, the Flavr Savr tasted fine; whether consumers still find it worth a dollar more per pound remains to be seen.Developing Pest Resistant PlantSeveral companies are hard at work on plants that will repel (抵制) pests (害虫). Monsanto, a St. Louis, Missouri, chemical company, expects to put many such products on the market before the end of the decade. The weapon of choice isBacillus thuringiensis, orBT, a soil-dwelling bacterium (细菌) that creates a protein crystal that is toxic to certain insects but harmless digested by humans.BT has been used for 30 years as an organic pesticide. Scientists can transfer the gene for the toxin into plant cells, and the new plants will produce their own insecticides. Like traditional insecticides, however, these
网考网参考答案：B
网考网解析：
根据文章第三段第六至七行，我们可以看出基因重组技术一旦成功，花生酱口味的胡萝卜的影像便开始跳跃在科学家们的脑海中。但这只是他们的大胆设想，还没有付诸实验，因此可推断出这种食品已上市的说法是错误的。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>