The invention of both labor-saving tools and tools of intelligence is rarely accidental. Instead, it is usually the product of h

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问题      The invention of both labor-saving tools and tools of intelligence is rarely accidental. Instead, it is usually the product of human need; (21) is truly the mother of invention. People usually devise tools to (22) for natural deficiencies. For example, people invented weapons to defend (23) from physically superior (24) . But (25) is only one incentive for inventions. People also invent (26) tools to (27) certain established tasks more efficiently. For instance, people developed the bow and arrow from the (28) spear or javelin in order to shoot (29) and strike with greater strength.
    (30) civilizations developed, greater work efficiency came to be demanded, and (31) tools became more (32) . A tool would (33) a function until it proved (34) in meeting human needs, at which point an improvement would be made. One impetus for invention has always been the (35) for speed and high-quality results--provided they are achieved (36) reasonable costs. Stone pebbles were sufficient to account for small quantities of possessions, (37) they were not efficient enough for performing sophisticated mathematics. However, beads arranged systematically evolved into the abacus. The (38) of this tool can be (39) to the development of commerce in the East around 3000 B.C., and the abacus is known (40) by the ancient Babylonians, Egyptians, Chinese, etc.


选项 A、to be used
B、to have used
C、to have been used
D、to use

答案C

解析 本题测试语法。本句话表示在过去的时间里已经完成的动作或存在的状态,所以应该用完成时态。B的语态不对。应该选C。
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