通信用-48V直流电源的“正极”在电源设备侧和通信设备侧均应（）。
A.接压敏电阻
B.接地
C.接避雷器
D.悬空
参考答案：B
There are altogether eleven books on the shelf,_________ five are mine. [ ]
A. on which
B. in which
C. of which
D. from which
确定T10，平面损伤的皮肤感觉区是（）
A.脐上4cm
B.脐上2cm
C.脐水平
D.脐下2cm
E.脐下4cm
