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.
Scientists have used papers in bottles to determine the number of______.

选项 A、beliefs about the experiments of the bottles
B、languages spoken along the course of the Gulf Stream
C、years needed for the Stream to make a complete trip
D、similar currents that have not yet been found

答案C

解析 文章倒数第二段中提到: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.“科学家们认为墨西哥湾暖流循环一次需要3年时间,这一结论是靠往暖流里投放塞着纸条的瓶子得出的”。因此,本题应选C。
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