For GMDSS，when may a compulsory vessel not

问题：

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