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  3. With the prospect of coal and petroleum supplies running out and with air pollution becoming an increasing concern, the major co

With the prospect of coal and petroleum supplies running out and with air pollution becoming an increasing concern, the major co

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问题     With the prospect of coal and petroleum supplies running out and with air pollution becoming an increasing concern, the major countries of the world are seeking alternate sources of energy. If a means to obtain energy from water, especially from the ocean, can be effected economically, it would provide a never-ending supply of energy, since 70% of the earth’s surface is ocean and another 10% is fresh water in rivers and lakes.
    From the beginning of time man has used waterpower as a source of working energy—waterfalls and dams—but these are fresh water sources and are landlocked. The seas have contributed little or nothing in the way of power. The use of temperature variation between currents is one area of exploration. Ocean water is heated by the sun near the equator and drawn by the rotation of the earth toward the poles, where it cools and drops toward the ocean floor and starts its journey back toward the equator. The differential between the two currents is l℃ and 7℃. To use it, the scientists must find the places where they run near land and are not too far away from each other.
    America, the greatest consumer of energy, has been working on another kind of thermal sea energy proposal. One plan would somewhat resemble the operation of a refrigerator on a vast scale. Warm water would be the heat source, cold water the heat sink. A component such as fog would be liquid at a cold temperature and turn to gas as it warmed.
    Oceans also offer wave power, tides and the chemical reaction of salt water as potential sources of energy. All these uses are theoretically possible. Britain is interested in wave power, using a string of "tear drop" devices that depend on very active wave areas at 100 feet depths. In addition to this, the British are working on a method that the Japanese have already put into practical use on a small scale for powering their navigational boats. This method is called an oscillating(振荡) water column and rides the waves with a series of cylinders(气缸) having one-way air valves. Wave movement produces air under pressure that has only one escape route—to a turbine(涡轮) that powers a generator.
选项 A、a new concept compared with other ways of natural resources
B、less expensive than petroleum and other means of energies
C、now being used more from the ocean than from rivers and lakes
D、being developed to supplement other sources of energy
答案D
解析 水作为能源是一种新的概念，而使用水作为能源由来已久，见第二段第一句，可知A选项是错误的。从文章第一段，尤其是第一段第二句可获知人类正试图利用水资源来弥补其他能量的短缺。D项为正确选项。B，C两项文中未涉及。
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