The word horsepower was first used two hundred years ago. James Watt had made the world’s first (11) used steam engine. He had

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问题 The word horsepower was first used two hundred years ago. James Watt had made the world’s first  (11)  used steam engine. He had no way of telling people  (12)  how powerful it was, for at that time there were no units for measuring power. Watt decided to  (13)  how much work one  (14)  horse could do in one minute. He called that unit one horsepower. With this unit he could measure the work his steam engine could do. He  (15)  that a horse could lift a 3, 300-potmd weight 10 feet into the air in one minute. His engine could lift a 3,300-pound weight 100 feet in one minute. Because his engine did ten times as much work as the horse, Watt called it a ten horsepower engine.
  

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答案exactly

解析 exactly意为“确切地”。
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