Most hydraulic steering gears are fitted with relief valves which（）
A. function when the rudder is amidships
B. relieve excess whip pressure from the hydraulic oil system
C. protect the piping assembly from external rudder shock
D. relieve excessive telemotor pressure
The Vessel Bridge-to-Bridge Radiotelephone Act applies to which towboat?（）
A 100 GT towboat，24 feet in length
B. A 90-foot towboat tied to the pier
C. A 60-foot towboat towing by pushing ahead
D. A 400 GT towboat anchored
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