For GMDSS,when may a compulsory vessel not be allowed to leave port?()
A、When the vessel is in an overloaded condition
B、When the vessel has arranged for both duplication of equipment AND shore-based maintenance
C、When the vessel has replaced a required piece of GMDSS-related equipment but its performance has not been verified or logged
D、When the vessel is carrying only two licensed GMDSS Radio Operators and is capable of performing all required functions