单项选择题 Certain requirements must currently be met by a ship’s steering system.There must be （）independent means of steering, although where two identical power units are provided, an auxiliary unit is not required.

单项选择题 In the variable delivery pump, moving the spindle more from the central point will cause （） fluid to be pumped and consequently （）pressure is generated to drive the rams.

单项选择题 The required rudder angle is transmitted hydraulically or electrically from the steering wheel at the bridge to the （）at the steering gear, just above the rudder.