Why should sound signals be used in restricted visibility?

Answer: B — For safety

Using sound signals in restricted visibility is primarily about safety. In conditions where visibility is limited—such as fog, heavy rain, or darkness—vessels may not be able to see each other, which increases the risk of collisions. Sound signals help to communicate a vessel's presence and intentions to others nearby, allowing for a more informed and cautious approach to navigation in these perilous situations. By performing sound signals like blasts or horn calls, vessels alert others to their position and movement, which is crucial when visual cues are unavailable. While the other options touch on important aspects of navigation and communication, the primary purpose in restricted visibility is enhancing safety by making the presence of vessels known to prevent accidents. Therefore, the focus on safety encapsulates the fundamental reason for employing sound signals under such circumstances.