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Nowadays more and more people care about the exploitation (开采） of the natural resources, such as oil. The_______ oil we use, the less these will be left for the future. Oil can be _______in many ways and it’s difficult to imagine what the modern world will be  _____ without oil. But oil isn’t easy to find and get out of the earth. Men must _______ the rocks, _______they think the rocks in a certain place may have oil, a metal tower is built. A machine in the tower  ______ a hole down into the ground. At the same time , a steel pipe （钢管） is pushed down to stop the sides from  ______ in and to keep out water. At last if the men are right, usually the oil rushes up high into the  _____. If the oil catches a light , there will be a terrible fire, ______a kind of cover is fixed on the top of the pipe. And the oil can run out through taps( 活塞）. Today the price of oil keeps rising all the time. In many countries, the governments encourage people to ____oil as much as possible.