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  3. All competitive ski and snowboarding events now take place largely on man-made snow. Unlike its natural counterpart, the machine

All competitive ski and snowboarding events now take place largely on man-made snow. Unlike its natural counterpart, the machine

admin2013-07-20  33
问题     All competitive ski and snowboarding events now take place largely on man-made snow. Unlike its natural counterpart, the machine-made white stuff can be carefully tweaked to make a more durable and consistent surface: one perfect for record-breaking attempts. Snow-making equipment is viewed as essential in most ski areas to guarantee coverage throughout the season. Nowadays, "natural snow is a bonus," says Rich Brown of snow-making technology company York Snow in Victor, New York.
    The snow "cannons" or "guns" that manufacture snow mimic the natural formation of snowflakes. Snow machines typically force pressurized water through a nozzle (喷嘴), breaking it into a mist of tiny droplets, and then use compressed air or fans to blast them into the air. As the droplets cool, the molecules line, and crystallize into ice particles. The art to snow-making is adjusting the water and air to ensure that the water drops are small enough and sent far enough that they will freeze before they hit the ground. If the air temperature is quite high, for example, dropping the water content and upping the air would create smaller particles that are more likely to freeze. Snow-making machines also frequently incorporate nucleating agents (成核剂)in the water： small quantities of materials such as bacterial protein, on to which the water molecules attach and freeze. By triggering freezing, these agents raise the temperature at which snow can be made.
    Many resorts now use sophisticated computer systems that automatically adjust the air and water output from snow machines based on air temperature, humidity and wind, says Brown. For race courses, experts adjust man-made snow to create a tough, fast and icy course rather than a powdery one. A ski course is also heavily groomed and often intentionally flooded to create patches of ice； these factors generally determine the speed of a race.
    Snow manufacturing is in great demand. Some predict that the need for snow will rocket with, the warming effects of climate change, which are already pushing snow lines up the Alps. But this comes with environmental costs, says Michel Revaz, of the International Commission for Protection of the Alps (ICPRA). Making snow chews up energy and water, and can rob rivers and creeks in the surrounding ecosystems. One way to conserve the mountain environment, Revaz says, would be to reuse winter sports competition facilities rather than building new ones.
The reason for the increasing demand of man-made snow may be attributed to______ .
选项
答案the warming effects of climate change
解析 细节辨认题。本题考查人造雪需求增加的原因。定位句明确指出，人造雪大有市场，接着提到这种需求在迅速增加，这与全球气候变暖有关。故答案为the warmingeffects of climate change。
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