2. 外语
  3. With the prospect of coal and petroleum supplies being depleted and with air pollution becoming an increasing concern, the major

With the prospect of coal and petroleum supplies being depleted and with air pollution becoming an increasing concern, the major

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问题     With the prospect of coal and petroleum supplies being depleted and with air pollution becoming an increasing concern, the major countries of the world are seeking alternate sources of energy. If a means to 【S1】______ energy from water, especially from the ocean, can be effected economically, it would furnish a never-ending supply of energy, since 70% of the earth’s surface is ocean and 【S2】______ 10% is fresh water in rivers and lakes.
    From the beginning of time man has used water power as a source of work from energy-waterfalls and dams, but these are fresh water sources and are landlocked. The seas have contributed 【S3】______ or nothing in the way of power.
    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 【S4】______ back toward the equator. The differential between the two currents is 35 degrees to 45 degrees Fahrenheit and to use it the scientists must find the places where they run near land and are not too far away from each other. One area that 【S5】______ these requirements is the Caribbean sea.
    One plan would somewhat resemble the operation of a refrigerator on a vast scale. 【S6】______ water would be the heat source, cold water the heat sink. A component such as Freon would be liquid at a cold temperature and 【S7】______ to gas as it warmed. Oceans also offer wave power, tides, and the chemical propensities of salt water as potential sources of energy. All these uses are 【S8】______ possible.
    The British are working on a method that the Japanese have already put into 【S9】______ use on a small scale for powering their navigational buoys. Wave movement produces air under 【S10】______ that has only one escape route to a turbine that powers a generator.

A) theoretically       B) turn            C) meets           D) needs
E) differently         F) warm            G) cold            H) journey
I) identifies          J) practical       K) critical        L) obtain
M) little              N) another         O) pressure
【S9】
选项
答案J
解析
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大学英语四级

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