Which maintenance functions can a GMDSS Radio Operator perform（）.
- AThe Operator can make fine internal adjustments to the transmitter as long as the output power does not change by more than one percent
- BThe Operator is responsible for ensuring that INMARSAT antennas are free of built-up soot and clear of obstacles
- CAll levels of maintenance must be performed by a licensed GMDSS Radio Maintainer
- DThe Operator may install an EPROM in order to ensure that the equipment continues to operate within legal constraint