题干
— Isn’t it amazing that I met my pen-friend Jim on May Day?
— Really? For how many years _______ each other?
A：didn’t you see
B：haven’t you see
C：hadn’t you see
D：don’t you see
答案(点此获取答案解析）
C
sin100πt(V)的交变电压，副线圈通过电阻r=6Ω的导线对“220V/880W”的电器RL供电，该电器正常工作。由此可知
