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