The correct answer is A) The Operator is responsible for ensuring that INMARSAT antennas are free of built-up soot and clear of obstacles. This is correct because as a GMDSS Radio Operator, the primary maintenance function is to ensure the GMDSS equipment is properly maintained and ready for use. This includes visually inspecting the INMARSAT antennas to ensure they are free of obstructions and debris that could interfere with their operation. The other answer choices are incorrect. B) is incorrect because GMDSS Radio Operators are allowed to perform certain maintenance functions, not just licensed GMDSS Radio Maintainers. C) is incorrect because Operators do not have the authority to install or modify EPROMs. D) is incorrect because Operators cannot make internal adjustments to the transmitter that would affect the output power.