线路轨距是指钢轨头部踏面下（）mm范围内两股钢轨工作边之间的最小距离。
A.10
B.16
C.8
D.6
参考答案：B
He goes to the park every evening, __ ? [ ]
A. is he
B. isn't he
C. does he
D. doesn't he
尿后余沥不尽的病机是（）
A.肾精亏虚
B.肾阴亏虚
C.肾气不固
D.膀胱湿热
E.肾不纳气
