六级冲刺备考的改错练习（9）

　　第九篇： Error Correction 　　Some people, in all seriousness, say that 　　humans will be living in space within the next 　　hundred or so years. Planet Earth will be crowded, 　　dirty and lack of resources. A sort of exodus --71. 　　of mankind will begin. 　　Spaceships will be assembled so that they 　　revolve around the earth. Some may orbit around 　　Mars. These space stations will be serviced by 　　space buses. We saw the first space bus launch in --72. 　　April 1981. This was Columbia, it made several --73. 　　orbits around the earth and then returned, landing 　　on a huge dry lake bed in California. Columbia 　　will be used again. previous spaceships have 　　been abandoned, only the nose cone being used 　　to bring the crews back to earth. --74. 　　Upon established, each space station will --75. 　　generate its own atmosphere and have its own 　　agriculture. it will need to rotation to provide --76. 　　an artificial gravity; people will be forced inwards --77. 　　from the center by centrifugal（向心的）force. 　　The moon and Mars could become new sources of 　　new materials. Driving through space will no --78. 　　longer need Earth fuel-the energy would come 　　from the sun. This energy would be converted from --79. 　　electricity to work magnetic rockets. 　　That all sounds quiet fantastically but, with --80. 　　the rapid development of modern technology, who 　　knows about what the future holds?