Which maintainance functions can a GMDSS Radio Operator perform?

A
The Operator can make fine internal adjustments to the transmitter as long as the output power does not change by more than one percent.
B
The Operator is responsible for ensuring that INMARSAT antennas are free of built-up soot and clear of obstacles.
C
All levels of maintenance must be performed by a licensed GMDSS Radio Maintainer.
D
The Operator may install an EPROM in order to ensure that the equipment continues to operate within legal constraints.
E