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对摄影条件选择公式 V=2d+C的解释,错误的是

A、该公式属于变动管电压法
B、管电压按被照体厚度改变
C、公式中C代表着可变数
D、公式中V代表欲选管电压
E、2d表示每增加1cm厚度,则增加2kV
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正确答案:

C

答案解析:

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