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f The Stratosphere C.The Sun’s Rays D.Recent Studies of The Upper Atmosphere Versus Past Studies E.The Definition And The Description of The Troposphere F.The Composition of The Atmosphere
参考答案： E 答案解析：
8Paragraph 3 _____.
A.The Definition and The Description of The Ions B.The Definition And The Description of The Stratosphere C.The Sun’s Rays D.Recent Studies of The Upper Atmosphere Versus Past Studies E.The Definition And The Description of The Troposphere F.The Composition of The Atmosphere
阅读理解
（第31—45题，每题3分，共45分;下面有3篇短文，每篇短文后有5道题。请根据短文内容，为每题确定1个最佳选项。）1、The Volcano Geologists have been studying volcanoes for a long time. Though they have learned a great deal, they still have not discovered the cause of volcanic action. They know that the inside of the earth is very hot, but they are not sure exactly what causes the great heat. Some geologists have thought that the heat is caused by the great pressure of the earth’s outer layers. Or the heat may be left from the time when the earth was formed. During the last sixty years scientists have learned about radium, uranium, thorium and other radioactive elements. These give out heat all the time as they change into other elements. Many scientists now believe that much of the heat inside the earth is produced by radioactive elements.Whatever the cause of the heat may be, we do know that the earth gets hotter the farther down we dig, in deep mines and oil wells the temperature rises about 10F for each 50 feet. At this rate the temperature 40 miles below the earth’s surface would be over 40000F. this is much hotter than necessary to melt rock. However, the pressure of the rock above keeps most materials from melting at their usual melting points. Geologists believe that the rock deep in the earth may be plastic, or puttylike, in other words, the rock yields slowly to pressure but is not liquid. But if some change in the earth’s crust releases the pressure, the rock melts. Then the hot, liquid rock can move up toward the surface.When the melted rock works its way close to earth’s crust, a volcano may be formed. The melted rock often contains steam and other gases under great pressure. If the rock above gives way, the pressure is released. Then the sudden expansion of the gases causes explosions. These blow the melted rock into pieces of different sizes and shoot them high in the air. Here they cool and harden into volcanic ash and cinders. Some of the material falls around the hole made in the earth’s surface. The melted rock may keep on rising and pour out as lava. In this way, volcanic ash, cinders and lava build up the cone-shaped mountains that we call volcanoes.
参考答案： A 答案解析：
1Which of the following statements is NOT true according to the passage?
A.Geologists know that volcano action is caused by radioactive elements. B.Geologists know that there is higher temperature within the earth. C.The real causes of the heat inside the earth have not been found. D.Scientists have made various guesses about the causes of heat inside the earth.
参考答案： D 答案解析：
2From the information given in the passage, most minerals would melt fastest _______.
A.at 40000F, at sea level B.at 40000F, 5000 feet below sea level C.at the exact center of earth at 40000F D.at 40000F, 5000 feet above the sea level
参考答案： A 答案解析：
3T
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