A 95-meter vessel aground must sound which fog signal?

A vessel that is aground is required to use specific sound signals to indicate its situation. The correct option involves a rapid ringing of a bell for 5 seconds, preceded and followed by three separate and distinct strokes on a bell. This sound signal is indicative of a vessel that is not able to maneuver and is also not under command.

The reason this option is correct is that it aligns with the International Regulations for Preventing Collisions at Sea (COLREGs), which outline the sound signals for various conditions at sea. The distinct pattern of sounds communicates to other vessels in the area that the aground vessel is unable to move and is presenting a navigation hazard.

The other choices, while they contain elements of sound signals, do not adequately convey the specific combination required for a vessel aground. For example, rapid ringing of a bell for 5 seconds every two minutes does not include the necessary sequences of distinct strokes that communicate the grounding situation. Similarly, whistle signals do not apply to an aground vessel, as these signals are more relevant for vessels that are able to maneuver. Thus, the selected answer reflects the correct action required by a vessel that is aground to ensure safety and awareness in the surrounding marine environment.