If you do not install the rigging pin, the elevators will move down when there is no pressure in the system. 如果不安装索具销，电梯将在系统没有压力时向下移动。
A.After the system is pressurized, the elevators will drop down no matter where the rigging pin is installed. B.Without the rigging pin, the elevators will go down when there is no pressure in the system. C.The rigging pin can prevent the elevators from retracting and expanding when the system is de-energized.正确答案B
