人体是_________________，根据欧姆定律，电压越高，通过人体的电流____________，所以电压越高越危险。人的皮肤干燥时比潮湿时的电阻____________，如果带电体接触的是潮湿的皮肤，通过人体的电流会____________，很危险，所以不能用湿手触摸电器。

—Why are you late for class again?        

—I was          to go back when the headmaster called us together.[ ]

A. about

B. able

C. used

D. supposed