塔吊的工作机构由（）组成。

A. you can stop within your visibility range
B. the vessel is not subject to vibrations
C. you are traveling slower than surrounding vessels
D. you can take proper and effective action to avoid collisio

A. 镗削内孔
B. 镗削外圆
C. 精车端面
D. 切槽
E. 切削内螺纹
F. 切削外螺纹