—Why are you so _______ Bill? —Because I heard an ________ news. A. excited exciting B. exciting excited B. C. exciting exciting D. Excited excited 答案:A由欧姆定律推导出R=U/I,下列说法中正确的是( )A.一段导体的电阻在通过它的电流不变时,阻值与它两端的电压成正比B.一段导体的电阻在它两端电压不变时,阻值与通过它的电流成反比C.一段导体的电阻与它两端的电压成正比,与通过它的电流成反比D.一段导体的电阻,等于它两端的电压与通过它的电流的比值