题目

We ____ our breath when our teacher read the final list. A. took             B. got          C. held         D. saved 答案：C 解析: 略如图所示，a、b两端电压恒定，电阻R1=2kΩ，用内阻也是2kΩ的电压表测电阻R1两端电压为2V，测R2两端电压为4V，则不接电压表时，a、b间总电压为 [     ]A．6V B．8V C．10VD．12V