在如图所示的电路中，开关S由断开到闭合时，电流表的示数由0.3A变化到0.5 A，此时滑动变阻器R₂消耗的电功率为4.5 W，则

A．通过电阻R₁的电流为0.2 A

B．滑动变阻器R₂连入电路的电阻值为50 Ω

C．电压表示数为15 V

D．1 min电阻R₁产生的热量为270 J

The traffic in the city          be terrible, but the city has improved a lot.  I think you will         it soon. 

A．used to;use to

B．get used to;used to

C．. used to; get used to

D．get used to; use to