无金属光缆最大的优点是()。
A、易弯曲
B、防潮性好
C、抗电磁干扰
参考答案:C
地下铁道有深埋式和()两种。
The little boy won't go to sleep __ her mother tells a story. [ ]
A. or
B. until
C. but
D. whether