图示直流电路，当R<sub>1</sub>=R<sub>2</sub>时，电阻R<sub>1</sub>两端电压为<img src="/Image1/03/03643a970b52d5a9f96ee1d060530635.jpg" />；当R<sub>1</sub>=2R<sub>2</sub>时，R<sub>1</sub>两端电压为<img src="/Image1/ca/ca13ae516c71adc783c1f0d4cc988f01.jpg" />，则<img src="/Image1/43/43cbb94374eaac41fe5c64be3e50195e.jpg" />等于（） <img src="/Image1/fe/feafcf958f3a68c3693dd334217e611b.jpg" /><br>A:2<br>B:<img src="/Image1/c3/c33a2d2eac1128b76c3ff94ff2dfad30.jpg" /><br>C:<img src="/Image1/e9/e9236d5a4f06f45a2576732802a6819d.jpg" /><br>D:<img src="/Image1/57/579351341723caee953b746f3c17dffe.jpg" />