___________ you know the donut?[ ]
A. Would
B. Do
C. Are
答案：B
—When did you come back?
—Half an hour ago. You ____ to music.
A．have been listening
B．were listening
C．had listened
D．listened
防雷设施及接地装置是（）。
A、将导线与杆塔绝缘
B、将导线与与大地连接
C、将电流引入大地
D、保护线路绝缘
