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问题 选择题

下图是一原电池的装置，关于它的说法正确的是 

[ ]

A．装置中铜是负极       

B．铜表面的反应为：2H++2e-=H2↑

C．电流的方向是从铁经导线流向铜

D．构成原电池后，铁与硫酸铜的反应速率加快

答案

答案：D

选择题
For many years, people _____ electric cars. However, making them has been more difficult than predicted.
A. had dreamed of
B. have dreamed of
C. dreamed of
D. dream of
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名词解释

电子枪
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