单项选择题
我们的重吊杆已经长时间不用了。（）
A. Our derrick has been out of use for a long time. B. Our heavy derrick has been out of use for a long time. C. Our crane has been out of use for a long time. D. Our winch has been out of use for a long time.
单项选择题 不要随意地移动稳索。（）
单项选择题 请调高一下吊杆。（）
单项选择题 吊杆停用时，稳索必须要收起来。（）
