单项选择题
A.78B.86C.68D.90
A.辙叉心轨尖端至心轨宽40mmB.辙叉心轨尖端至心轨宽50mmC.辙叉心轨尖端至心轨宽30mmD.辙叉心轨尖端至心轨宽20mm
A.45~49B.43~49C.45~47D.42~49