What is the antenna requirement of a radiotelephone installation aboard a passenger vessel?

The correct answer highlights that the antenna used in a radiotelephone installation aboard a passenger vessel must be vertically polarized and efficient for seawater communication. This specification is crucial because vertical polarization helps optimize signal strength and reception in maritime environments where seawater can significantly impact signal propagation. The efficiency of the antenna in this context is essential for ensuring reliable communication over long distances, especially given the unique challenges posed by the maritime environment, such as reflective surfaces and interference from the ocean.

The emphasis on seawater communication quality also speaks to the operational needs of vessels at sea, where clear and dependable communication channels are vital for safety and navigation.

Other choices, while they may present relevant information, do not specifically address the primary requirement regarding polarization and communication efficiency tailored to the maritime context. This focus on the antenna's characteristics ensures that the installation meets the operational requirements set forth by maritime communication standards.