问题：

[单选] Which maintenance 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 constraint