题目

Are you having difficulty falling asleep? Try drinking a glass of warm milk. If that doesn't work, listen to soft, beautiful music. Still no luck? Try thinking about sheep jumping over a fence. If you are still awake, take a sleeping pill. But people who take pills often become dependent on the drugs. So you lie awake knowing that the new workday will soon arrive. If you have been in such condition for at least one month, you may have primary insomnia(失眠症)． A new study has found that you might fall asleep more quickly and stay asleep longer if you try “cerebral hypothermia”.如图所示，电源电压不变，当开关S闭合时，电流表示数是1A；当开关S断开时，电流表示数是0.6A，则与的阻值之比是 [　　] A．3∶2 B．2∶3 C．5∶3 D．3∶5