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