S700K转辙机上层检测杆用于（）的工作状态。
参考答案：监督缩进密贴的尖轨
Jack doesn’t look ___ his father, but he walks ___ his father does.
A．as; as
B．as; like
C．like; likes
D．like; as
管道安装前应具备哪些条件？
