---How long did you skate, Kate? --- I skated ________ two hours. A. in B. at C. since D. for 答案:D说出下列过程中能量转化或转移的情况
(1)启动汽车的发动机,汽车向前开_____________________________________
(2)滑滑梯时,臀部会发烫_____________________________________________
(3)利用电饭锅烧饭_____________________________________________
(4)十字路口的给红绿灯提供电的太阳能电池板__________________________