题目内容
Henry James is generally regarded as the forerunner of the 20th-century "______" novels and the founder of psychological realism.
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T.S. Eliot’s ______ is the best of his plays in the sense that it contains the best poetry and the most coherent drama.
测量系统的灵敏度与鉴别阈、显示装置的分辨力和鉴别阈有何区别
什么是测量仪器的测量不确定度
A lot of people think we could be headed for trouble by tampering with Mother Nature and producing genetically altered food. But those who promote genetically modified foods say it"s no more unnatural than traditional selective breeding, to say nothing about synthetic fertilizers and chemical pesticides.Most Canadians regularly eat bioengineered food. Anyone who consumes cheese, potatoes, tomatoes, soybeans, corn, wheat, and salmon is taking in genetically modified (GM) food. In addition, 75 % of processed foods contain GM ingredients. In fact, around 65% of the food we get from the shops has some genetically modified component. GM food does not have to be labeled as such in Canada, so most of us don"t know we"re eating it. Some of the items that have a high likelihood of containing GM material might surprise you. They include chocolate bars, baby food, margarine, canned soup, ice cream, salad dressing, yogurt, cereals, cookies, and frozen French fries. And, there"s nothing new about this.Farmers and plant breeders have used genetically modified foods for centuries; if they hadn"t, we"d probably still be eating grass instead of wheat. They"ve refined the foods we eat through selective crossbreeding, combining different types of wheat, for example, and eliminating weaker varieties. Today, genetic engineering is changing the nature of plant breeding even more: it"s no longer just a case of mixing different varieties of the same species. Now, genes from completely different life forms are being combined-fish genes into tomatoes to make the latter more frost resistant, for example.Such "tampering with Nature" makes a lot of people anxious. They wonder if the foods that come out of genetic modification are safe for human consumption. Scientists say they are completely safe; GM is just a way of adding genes to plants to make it possible for them to survive without the use of pesticides and to increase yields. But, the non-believers point out that scientists said that nuclear power, the toxic insecticide DDT, and a host of other things, were also completely harmless.Fans of agricultural biotechnology think producing GM food is a move in the right direction, that it will ultimately improve health, the environment, and the economy. They"re convinced it will solve the world"s hunger problems by boosting the nutritional content of foods, lead to a drop in pesticide and herbicide use, and result in more efficient and profitable farming. Critics say it could also create superweeds and insects, disrupt global food systems, destroy ecological diversity, put small farms out of business, and cause long-term environmental problems. All that aside, they think consumers have a right to know what is in their food.After all, GM products do pose some problems. In 1998, a researcher at the Rowett Institute for Agriculture in Aberdeen announced to the world that genetically engineered potatoes did some nasty things to the rats they were tested on. The potatoes were engineered to produce a molecule which is a natural insecticide that makes them resistant to aphids. But, the rats that ate the potatoes didn"t grow as large as normal rats and were less resistant to disease. Further research showed that the added gone wasn"t the only cause for concern: the genetic-engineering process itself was causing some serious problems in the development of organs such as the kidney and spleen.Some genetic modifications have been clearly beneficial. For example, one variety of maize has been genetically manipulated to produce a natural insecticide that protects it from the corn-borer moth. Scientists have also developed GM soybeans which are not damaged by some common herbicides used to kiI1 weeds. What is more, the rats that were fed GM potatoes may not have been harmed as a result of the genetic modification but possibly as a result of the way the potatoes were gown; all in all, there are just too many variables to blame the genetic-engineering process alone. Still, some believe that the potential problems with gene modification are so well known that existing safeguards, in both America and the European Union, can prevent them.Supporters of GM foods look on the bright side. According to the International Service for the Acquisition of Agri-biotech Applications (financed largely by biotechnology firms) the insect-resistant maize has increased yields in fields where it is planted by 9%. And, there might be an environmental advantage too. In 1997, 2.8 million hectares of the variety of maize were planted in the U.S. and farmers were able to avoid using $190 million worth of insecticide. Herbicide-resistant soybeans also needed less spraying, pumping between 20% and 40% fewer chemicals into the environment.Using NO MORE THAN THREE WORDS OR A NUMBER from the passage, answer the following questions. What chemical substances may be less necessary as a result of the genetic modification of agricultural products
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