The environmentalists said wild goats' _____ on the vast grasslands was a good indication of the better

environment.[ ]

A. escape

B. absence

C. attendance

D. appearance

最高行车速度不超过无列检作业时，站内正线和与其相邻到发线在直线部分的标准距离是（）mm。

A.4000

B.5000

C.5300

D.5500