单项选择题

案例分析题

Space is filled with radiant energy and beyond earth’s atmosphere this energy flow steadily and intensely from the sun. An abundant and essential (67) of energy would be used in space by developing satellite solar (68) stations. To live in space, humans must be protected (69) the fierce intensity and penetrating sunlight. The colony will have to have enough energy to (70) a fairly uniform temperature. The sun is not dimmed (71) an atmosphere. Shaded materials not (72) to direct sunlight will almost be absolute zero, while the temperature can soar above the (73) point. The colony will need to have both heaters and (74) Fortunately, sun’s energy can be converted (75) electricity. Converting sun’s energy, we would (76) stations in the space that would intercept (77) sunlight. The stations intercept enough sunlight to (78) five nuclear reactors and they could be as (79) as nine miles long and four miles wide while they weigh twenty thousand tons. This is a (80) free way to generate electricity and cost no (81) than coal or nuclear energy. Solar cells do the actual converting. A useful material found in lunar soil is silicon which is used to make solar cells. (82) we can produce a large amount of these cells and then we avoid any problems of (83) the material from earth. A solar cell is made from two thin layers of silicon. Sunlight (84) on the cell shakes the electrons (85) , and then these electrons move off into an outside circuit, which is detected as an electrical current. Things are arranged (86) most of the work involved in generating the electricity is done by forces associated with the atoms themselves.

86（）

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