If the sun has enough【C1】______to warm and light the whole earth, it must have enough power to do other things,【C2】______. Can w

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问题    If the sun has enough【C1】______to warm and light the whole earth, it must have enough power to do other things,【C2】______. Can we use the sun’s【C3】______energy to supply electricity, or at least to perform the function which electricity or other types of power usually perform? The answer is【C4】______.
   For example, people have for many years been using the【C5】______heat of the sun to cook by solar【C6】______which have been built with several incurred【C7】______reflecting the sun and focusing the heat on the cooking element. This【C8】______can be used like a gas or electric stove; it is more expensive to make but it doesn’t need any【C9】______and so costs【C10】______to use. Another【C11】______of using solar energy is in house heating.
   The【C12】______of energy we use most is electricity, and every day more is【C13】______. But electricity has to be made too, and to make it huge quantities of fuel is required -- oil, coal, gas and nowadays even uranium.
   The question which【C14】______everyone today is: how long will these fuels【C15】______? Nobody knows it for sure,【C16】______most experts think it will soon be difficult to obtain sufficient electricity from these sources. It is possible that the sun can make a(n)【C17】______here, too.
   Solar power has already been used to produce【C18】______heat. In Southern France a solar furnace has been built,【C19】______temperatures reach more than 3 000 centigrade. This furnace is not only used for experiment【C20】______, but could be used to produce steam for a power station.
【C15】

选项 A、stop
B、produce
C、work
D、last

答案D

解析 考查动词辨义与上下文理解。stop停止,停下,阻止;produce生产,产生,work工作,起作用; last持续。由空格前的how long(多久)可知应选last。
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