单项选择题
A.hydraulic steering
B.follow-up steering
C.remote control steering
D.air controlled steering
单项选择题 （） is used for sensing the temperature of the room in the air condition system.
单项选择题 The control spindle operates the slipper ring or （） of the variable delivery pump, which controls the suction and discharge of the oil.
单项选择题 Where tanks are arranged for either oil or ballast, （） must be fitted in the pipeline.