题目

如图所示的U—I图象中，I是电源的路端电压随电流变化的图象，Ⅱ是某电阻两端的电压随电流变化的图象，当该电源向该电阻供电时，电阻上消耗的功率和电源的效率分别为                                                      （     ） A．4 W和33.3%                      B．2 W和67% C．2 W和33.3%                      D．4 W和67% in the adult ceremony，the senior students feel they are shouldering heavier responsibilities now.A. Swear B. SwornC. Having sworn D. To have sworn