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如图所示,电源两端的电压保持不变,R1为定值电阻.将滑动变阻器的滑片P置于最右端,闭合开关S.移动滑动变阻器的滑片P到某一位置,此时滑动变阻器接入电路中的电阻为R2,电压表V1、V2的示数分别为U1、U2,此时电路中的电流为I;继续移动滑动变阻器的滑片P,使滑动变阻器接入电路中的电阻值变为R2′,此时电压表V1、V2的示数分别变为
U
1
2
3
2
U2,此时电路中的电流为I′.则下列说法中正确的是(  )
 

A:I:I′=1:2

B:R1:R2=1:1  

C:R2:R2′=1:1 

D:U1:U2=2:1

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B

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