03-14 12:38:20 浏览次数: 949
Experiments under way in several labs aim to create beneficial types of genetically modified （GM） foods, including starchier potatoes and caffeine-free coffee beans. Genetic engineers are even trying to transfer genes from a cold-water fish to make a frost-resistant tomato.
A low-sugar GM strawberry now in the works might one day allow people with health problems such as diabetes to enjoy the little delicious red fruits again. GM beans and grains supercharged with protein might help people at risk of developing kwashiorkor, Kwashiorkor, a disease caused by severe lack of protein, is common in parts of the world where there are severe food shortages.
Commenting on GM foods, Jonathon Jones, a British researcher, said: “The future benefits will be enormous, and the best is yet to come.”
To some people, GM foods are no different from unmodified foods. “A tomato is a tomato,” said Brian Sansoni, an American food manufacturer.
Critics of GM foods challenge Sansoni’s opinion. They worry about the harm that GM crops might do to people, other animals, and plants.
In a recent lab study conducted at Cornell University, scientists tested pollen made by Bt corn, which makes up one-fourth of the U. S. corn crop. The scientist sprinkled the pollen onto milkweed, a plant that makes a milky juice and is the only known food source of the monarch butterfly caterpillar. Within four days of munching on the milkweed leaves, almost half of a test group of caterpillars had died. “Monarchs are considered to be a flagship species for conservation, ”said Cornell researcher Linda Raynor. “This is a warning bell.”
Some insects that are not killed by GM foods might find themselves made stronger. How so? The insecticides used to protect most of today’s crops are sprayed on the crops when needed and decay quickly in the environment. But GM plants produce a continuous level of insecticide. Insect species feeding on those crops may develop resistance to the plants and could do so in a hurry, say the critics. Insects may also develop a resistance to the insecticide Bt.
At the forum on GM food held last year in Canada. GM crops that have been made resistant to the herbicide might crossbreed with wild plants, creating “superweeds” that could take over whole fields.
So where do you stand? Should GM foods be banned in the United States, as they are in parts of Europe? Or do their benefits outweigh any of the risks they might carry?
1. Paragraphs 1, 2 & 3 tries to give the idea that
A. GM foods may bring about great benefits to humans.
B. we cannot recognize the benefits of GM foods too early.
C. GM foods may have both benefits and harm.
D. GM foods are particularly good to the kwashiorkor patients.
2. Why is the case of the pollen-sprayed milkweed cited in Paragraph 6?
A. It is cited to show GM foods can kill insects effectively.
B. It is cited to show GM foods contain more protein.
C. It is cited to show GM foods also have a dark side.
D. It is cited to show GM foods may harm crops.
3. What happens to those insects when not killed by the spray of insecticide?
A. They may lose their ability to produce offspring.
B. They may have a higher ability to adapt to the environment.
C. They move to other fields free from insecticide.
D. They never eat again those plants containing insecticide.
4. Which of the following statements concerning banning GM foods is true according to the passage?
A. Underdeveloped countries have banned GM foods.
B. Both Europe and the U. S. have banned GM foods.
C. Most European countries have not banned GM foods.
D. The United States has not banned GM foods.
5. What is the writer’s attitude to GM foods?
A. We cannot tell from the passage.
B. He thinks their benefits outweigh their risks.
C. He thinks their risks outweigh their benefits.
D. He thinks their benefits and risks are balanced.