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问题 单项选择题

在进行保护管配管时，要注意保护管内径和管内穿的电缆数。通常电缆的直径之和不能超过保护管内径的（）。

A.1/3

B.1/2

C.2/3

D.1/4

答案

参考答案：B

问答题

如图所示，一摆球的质量为m，带正电荷，电量为q，摆长为L，场强E=

mg
q
，水平向右，摆球平衡位置在C点，与竖直夹角为θ，开始时在水平位置A点，无初速释放，求摆球在C点时的速度及摆线的拉力．
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单项选择题

As we have known from the map of the woad, this is ______.

A．twice as large an island as that
B．twice as larger as that island
C．as twice as that one
D．twice as a large island as that
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