The Gulf Stream, which runs like a friendly blue river across the cold green Atlantic Ocean, is one of the mightiest powers in t

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问题     The Gulf Stream, which runs like a friendly blue river across the cold green Atlantic Ocean, is one of the mightiest powers in the worlD. By comparison, the Mississippi and the mighty Amazon are but small rivers. Two million tons of coal burned every minute would not equal the heat that the Stream gives forth in its Atlantic crossing. Without the Stream’s warmth England’s pleasant green countryside would be as cold as Labrador, which is no farther north than EnglanD. If this "river of blue" were cooled as much as 15 degrees, England, Scandinavia, northern France and Germany would probably become a region for the Eskimos.
    The general course of the blue river has never been known to change. From Florida north the Stream follows the curve of the coast but stays well away from the shore. When the warm waters meet the icy Labrador currents, the Stream loses some speed and heat, but even with icebergs at its margin it stays warm enough for tropical sea life.
    As the Stream nears Europe it divides north and south. The northern drift mixed with the Arctic Ocean. The southern drift comes again into the path of Africa’s hot trade winds, and the waters hurry back to the Gulf of Mexico, gathering again their store of heat. The complete course of the Stream, therefore, is like a tremendous 12,000-mile whirlpool.
    Scientists think that it takes three years for the Stream to make a complete trip. Their belief is based on the courses of bottles that have been thrown into the Stream to drift. These bottles contain papers, printed in many languages, requesting the finders to note the places and dates of finding and mail them back. Government experts on ocean currents have records of thousands of there "bottle papers".
    Other oceans have such currents. In the North Pacific, for example, the Japanese Current makes the climate of coastal Alaska and America’s west coast milD. Science is still not satisfied with what it knows about these currents. But for most of us it is enough to know that the Gulf Stream and similar currents give warmth to countries that would otherwise be very cold indeed.
The phrase that best expresses the main idea of this selection is______.

选项 A、interesting facts about the Gulf Stream
B、scientific experiments on the Gulf Stream
C、currents similar to the Gulf Stream
D、tropical sea life in the Golf Stream

答案A

解析 显然全文都是在介绍关于墨西哥湾暖流的一些情况,但并不涉及热带海洋生物。科学实验也只是其中的一部分内容;虽然文章最后也提到了日本暖流,但这并不属于全文的中心内容。因此,只有A项正确。
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