单项选择题
A.(tz一20℃)~(tz+20℃) B.(tz一25℃)~(tz+25℃) C.(tz一30℃)~(tz+30℃) D.(tz一35℃)~(tz+35℃)
A.长度超过50mm,深度超过8mm B.长度超过30mm,深度超过10mm C.长度超过30mm,深度超过8mm D.长度超过50mm,深度超过10mm
A.综合维修 B.经常保养 C.临时补修 D.线路中修