Final answer:
In Alabama, if a vessel is towing a skier without an observer on board, it must have a rearview mirror for the operator to monitor the skier, ensuring their safety.
Step-by-step explanation:
According to Alabama law, when a vessel not classified as a Personal Watercraft (PWC) is towing a skier without a capable observer on board besides the operator, it must be equipped with a rearview mirror. This mirror should be in place to allow the operator to observe the person being towed at all times, effectively serving as the eyes in the absence of a dedicated observer. This requirement ensures the safety of the person being towed, as the operator can maintain direct supervision and react promptly to any situations that may occur while the vessel is in motion.