Which of the following statements concerning GMDSS maintenance requirements is true?
The options are duplication of equipment, at-sea maintenance, and shore-based maintenance.
Compulsory vessels between 300-500 gross tons are required only to provide one maintenance option, while compulsory vessels larger than 500 gross tons and all passenger vessels are required to provide any two of the three maintenance options.
The "at-sea" maintenance may be waived if the compulsory vessel carries at least three licensed GMDSS Radio Operators.
Compulsory vessels operating in Sea Area A4 are required to carry at least one licensed GMDSS Radio Maintainer.