变压器过负荷时报预告信号。
参考答案：对
If a person has not had enough sleep,his actions will give him ___ during the day.[ ]
A. out
B. up
C. in
D. away
160km/h及以下区段接触网的之字值安全值不得大于（）。
A、400mm
B、450mm
C、475mm
D、500mm
