更换截齿时，将采煤机放置在顶板完整的位置，对滚筒前后共计三架进行逼帮防护。
参考答案：对
— Oh, this is really a small old town.
— Do you know when it ______? [ ]
A. built
B. was built
C. has built
D. has been built
机械制图基本幅面，图标A3纸的尺寸为210297mm。
