问题
单项选择题
A tackle by which the outer end of a boom is raised and lowered is the topping（）.
A.boom
B.lift
C.raise
D.tackle
答案
参考答案：B
搜题请搜索小程序“爱下问搜题”
A tackle by which the outer end of a boom is raised and lowered is the topping（）.
A.boom
B.lift
C.raise
D.tackle
参考答案：B