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  3. These days, many large city buildings are equipped with their own air-conditioning systems. These systems help keep the building

These days, many large city buildings are equipped with their own air-conditioning systems. These systems help keep the building

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问题     These days, many large city buildings are equipped with their own air-conditioning systems. These systems help keep the buildings cool, but they can also damage the environment. Since they use a lot of electricity, for instance, they contribute indirectly to global warming. In addition, the water that flows through the systems is often cooled using chemicals called chlorofluorocarbons, or CFCs, that are believed to damage the Earth’ s ozone layer. Recently, though, a system has been built in the city of Toronto, Canada, that cools buildings with little damage to the environment.
    In the traditional air-conditioning systems found in most large buildings, water is pumped through the building in a continuous cycle. The water is first cooled to a temperature of 4°C in machines called chillers. It is then sent to individual units that cool the air in each room. As the water flows through the building, it gradually becomes warmer. Finally, it reaches the roof, where it is left to cool down naturally in a water tower. After that it is returned to the chillers, where the cycle begins again.
    Toronto lies on the shore of Lake Ontario, one of North America’s Great Lakes, and the new system makes use of cold water taken from about 80 meters below the surface of the lake. At this depth, the water in the lake remains at 4°C all year round. This is exactly the temperature to which the water in air-conditioning systems is cooled. However, the water from the lake is not pumped directly into the air-conditioning systems. Instead, it is used to cool the water that is already inside the air-conditioning systems. After that, the lake water is added to the city’s ordinary water supply.
    Enwave, the company that developed this deep-lake cooling system, says that it uses 75 percent less energy than traditional air conditioning. And since no CFCs are used, no damage can be caused to the ozone layer. Not every city is located next to a large lake, but experts believe that systems like the one being used in Toronto could be built elsewhere by using other natural sources of cold water.
Which of the following is true?
选项 A、Enwave’ s system is said to work only in cities located near the Great Lakes.
B、The water deep in Lake Ontario always remains at the same temperature.
C、Experts warn that the use of CFCs in Enwave’ s system will add to global warming.
D、Toronto is now searching for new natural sources of water to use in its water supply.
答案B
解析 细节题。细节题。根据短文第三段第二句中At this depth，the water in thelake remains at 4℃all year round．可知选项B正确。根据短文最后一句but expertsbelieve that systems like the one being used in Toronto could be built elsewhere by usingother natural sources of cold water可知选项A、D错误；根据短文第二、三段可知Enwave’s system不使用CFCs，故排除C。所以选B。
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