The word horsepower was first used two hundred years ago. James Watt had made the world’ s first【B1】______used steam engine. He

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问题     The word horsepower was first used two hundred years ago. James Watt had made the world’ s first【B1】______used steam engine. He had no way of telling people【B2】______how powerful it was, for at that time there were no units for measuring power. Watt decided to【B3】______how much work one【B4】______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【B5】______that a horse could lift a 3,300-pound 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.
【B2】

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答案exactly

解析 exactly意为“确切地”。
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