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电源与外电阻R连接成闭合回路,对于电源的路端电压U,下列说法正确的是(   )

A:因U=IR,则U 与R的大小成正比

B:因U=IR,则R=0时,必有U=0

C:流过电源的电流越大,路端电压U也越大

D:若外电路断开,回路中电流为0,路端电压也等于0

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B

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