there are different ways in which people try to deal with the problem of energy.one way is the greater production of common energy sources, such as coal, oil and gas.the trouble with these sources, however, is that they are not renewable.another way is energy conservation（节能）, which means using energy more efficiently.in some very cold countries people build special houses to save energy.they place materials between the inside and the outside of the walls of the house to keep the cold out and the warmth in.the house is heated by the lights, the body heat of the people and the other equipment in it.finally, renewable energy sources are used even though they are often expensive to develop.one form of these is geothermal energy.in certain parts of the world the temperature of the earth increases thirty degrees centigrade with each kilometer down.at six kilometers, therefore, it rises to nearly two hundred degrees.to get the heat, water is pumped（压:抽）down into the rocks and back up to the surface.heat from the earth is already used in certain countries.54.How many ways of dealing with the energy problem are discussed in the text?（）A.TwoB.ThreeC.FourD.Five55.From the text we learn that coal（）.A.is quite easy to produceB.is not used most fficientyC.is the most common source of energyD.could be renewed only by new technology56.The writer tells about the "special houses" because they（）.A.show the excellent skils of the buildersOB.serve as an example of energy conservationC.are heated by dferent soures of energyD.are warmer than other types of houses57.The underlined words geothermal energy in the third paragraph mean（）.A.renewable sourceB.underground sourceC.heat inside the earthD.temperature of the earth58.at a place where the surface temperature is 15°C, how deep do you have to dig so as to get a temperature of 75°C?（）A.One km.B.Two km.C.Three km.D.Four km