关于电流、电压、电阻三者的关系，下列说法中正确的是（　　）

A．有电压就一定有电流，因为电压使电路中形成了电流

B．导体两端的电压随电流而改变，并成正比

C．加在同一导体上的电压增大几倍，通过导体的电流也会增大几倍

D．当电流增大2倍时，导体的电阻也增大2倍

______ for a few days, the thirsty and hunger soldiers had to give in at last.

A．Being surrounded

B．Surrounding

C．Having been surrounded

D．Having surrounded