钢柱田野基础标高要低于轨面()。
A、100~200mm
B、200~300mm
C、100~300mm
D、200~500mm
参考答案:D
He visited Shanghai _____ he went to China. [ ]
A. at the first time
B. the first time
C. for the first time
D. at the first time when
请简述简单悬挂导线安装曲线的绘制步骤。