When Inmarsat-B and Inmarsat-C terminals are compared:

Correct Answer: Option D — None of the above

Inmarsat-B uses high-gain, directional parabolic antennas to support voice and high-speed data, while Inmarsat-C uses low-gain, omni-directional antennas for messaging. Since neither description in the options correctly matches these fundamental technical characteristics, 'None of the above' is the only accurate choice regarding their antenna design and gain properties.