家庭电路中各盏照明灯是_______联的；如图所示，人们用试电笔辨别火线和零线的两种使用方法中，正确的是_______。
并；甲
—I didn't go to see the doctor yesterday.
—But you ________.
A．ought
B．ought to
C．ought to be
D．ought to have
