What does Rule 22 define?

Answer: B — Signals for vessels engaged in specific activities

Rule 22 specifically deals with the signaling requirements for vessels engaged in various activities at night or in reduced visibility. This rule outlines the specific shapes and lights that a vessel must display to signify its current activity or status, such as whether it is at anchor, constrained by its draft, or engaged in fishing. Proper signaling is essential for ensuring that other vessels are aware of a ship's activities, promoting safety and preventing collisions on the water. The other choices, while related to maritime operations and safety, do not pertain to the specific content of Rule 22. Safety measures for crew at night and responsibility for collision avoidance involve broader safety protocols and the responsibilities of vessels under various circumstances, and requirements for vessel maintenance are governed by different regulations not covered by Rule 22. Thus, understanding the specific signaling requirements outlined in Rule 22 is crucial for maintaining safe navigation practices.