Computers may one day turn night into day—with good old, natural sunlight. Colossal computer-controlled mirrors, thousands o

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问题     Computers may one day turn night into day—with good old, natural sunlight.
    Colossal computer-controlled mirrors, thousands of feet across, may one day orbit the earth, reflecting sunlight onto a darkened United States.
    Some scientists say that 16 of these mirrors, each about a half mile across, could aim their reflected light at one area on the earth that was about 200 miles by 300 miles. That much light would equal about 56 moons.
    The mirrors would be so high that they could catch the sun’s light as it was shining on the other side of the earth. The mirrors could orbit—thousands of miles high—at the same speed as the earth turns on its axis. That way, the mirrors would always be over the same spot. The aluminium-coated, plastic mirrors could be folded up and packed into a spaceship, according to the scientists. Once released a few hundred miles in space, the mirrors, powered by a solar-powered engine, could make the rest of the trip into space on their own.
    The scientists say that the computer-controlled mirrors could also be made to tilt slowly so the reflected sunlight would sweep slowly along the surface of the earth. For example, as night fell, the mirrors could be tilted to light up Boston. Later on, as darkness spread slowly westward, Chicago, for example, then San Francisco could be lit up. The reflected sunlight would allow these cities to save up electricity. And in emergencies, such as power-failures, the mirrors could light up the affected area.
    What no one knows yet is what effect this artificial daytime would have on plants, animals, and humans. Would it confuse some animals and harm plants that are used to regular day-night cycles? The scientists recommend that studies be done to find out what bad effects there might be.
The reflected light would sweep slowly along the surface of the earth because the mirrors

选项 A、would be operated by solar-powered engines
B、could be made to adjust their angles
C、could move around the earth at the same speed as the earth turns on its axis
D、would orbit thousands of miles high to catch the sun’s light

答案B

解析 本题是一道具体细节题。问反射的太阳光线可以慢慢扫过地球表面的原因是什么。文章第五段指出,科学家们说,计算机控制的镜面还可以缓慢倾斜,使反射的阳光缓慢地沿地球表面扫过。比如,当夜幕降临时,经倾斜的镜面可以照亮波士顿,稍后,随着夜色的逐渐西移,可照亮芝加哥,然后照亮旧金山。因此,本题的正确答案应是B“因为这些反射镜可以调整其倾斜角度”。
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