A:had only talked
B:am only talking
C:have just talked
D:was just talking
55+4=____
55+40=____
77-2=____
77+20=____
55-4=____
55-40=____
77+2=____
77-20=____
请用笔画线代替导线在图中连接家庭电路。要求开关控制螺口灯泡,三孔插座直接接入电路。