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Biotechnologists have developed genetically modified rice that is fortified with beta-carotene which the body converts into vitamin A and additional iron, and they are working on three kinds of nutritionally improved crops. Biotech can also improve farming productivity in places where food shortages are caused by crop damage attributable to pests, drought, poor soil and crop viruses, bacteria or fungi. Damage caused by pests is incredible. In trials of pest-resistant cotton in Africa yields have increased significantly. So far, fears that genetically modified, pest-resistant crops might kill good insects as well as bad appear unfounded. Viruses often cause massive failure in staple crops in developing countries. Two years ago Africa lost more than half its cassava crop — a key source of calories — to the mosaic virus. Genetically modified, virus-resistant crops can reduce that damage, as can drought-tolerant seeds in regions where water shortage limits the amount of l
A. biotech is the only solution to lack of food
B. biotech is still very hard to be used by the poor farmers in the developing world
C. biotech is more crucial to wealthy countries than developing countries
D. the risks of biotech outweigh the benefits

[单项选择]

Biotechnologists have developed genetically modified rice that is fortified with beta-carotene which the body converts into vitamin A and additional iron, and they are working on three kinds of nutritionally improved crops. Biotech can also improve farming productivity in places where food shortages are caused by crop damage attributable to pests, drought, poor soil and crop viruses, bacteria or fungi. Damage caused by pests is incredible. In trials of pest-resistant cotton in Africa yields have increased significantly. So far, fears that genetically modified, pest-resistant crops might kill good insects as well as bad appear unfounded. Viruses often cause massive failure in staple crops in developing countries. Two years ago Africa lost more than half its cassava crop — a key source of calories — to the mosaic virus. Genetically modified, virus-resistant crops can reduce that damage, as can drought-tolerant seeds in regions where water shortage limits the amount of l
A. The genetically modified, pest-resistant crops might kill good insects as well as bad ones.
B. It can help solve the problem of soil that contains little aluminum.
C. It could overcome the challenge of distributing food in developing countries.
D. It can help prevent the loss of those crops before they are harvested.

[单项选择]Large animals living in the desert have developed a number of adaptations for reducing the effects of extreme heat. One adaptation is to be light in color, and to reflect rather than absorb the sun’s rays. Desert animals also depart from other animals’ normal practice of maintaining a constant body temperature. Instead of trying to keep down the body temperature deep inside the body, which would involve the loss of water and energy, large desert animals allow their temperatures to rise to what would normally be fever height, and temperatures as high as 46 degrees Celsius have been measured in grant’s gazelles. The over-heated body then cools down during the cold desert night, and indeed the temperature may fall unusually low by dawn, as low as 34 degrees Celsius in the camel. This is an advantage since the heat of the first few hours of daylight is absorbed in warming up the body, and an excessive buildup of heat does not begin until well into the day.
Another strategy of large
A. How large desert animals adapt to the environment.
B. Weather conditions in the desert.
C. Human use of large desert animals.
D. Health problems of large desert animals.

[单项选择]Scientists have developed a slimming drug after years of efforts．The drug can successfully (62) appetite and result (63) a dramatic loss of weight without any apparent ill effects．
The drug (64) appetite control and, as a result, (65) the build-up of fatty tissue．Laboratory mice given the drug (66) up to a third of their total body weight．
Within 20 minutes of (67) the drug, called C75, the mice lost interest in eating and survived apparently content on just 10 percent of the food they would (68) eat． More (69) , the drug appears to prevent a serious (70) in metabolic rate- (71) tiredness and sleepiness which is typically (72) with living on a starving diet．
As a result, mice taking the drug lost 45 percent (73) weight than mice fed the same amount of food, which compensate (74) the lack of food by becoming (75) in moving around．

A. prevents
B. causes
C. increases
D. harms