What sound signal must a vessel planning to overtake another vessel at a safe distance use?

Answer: C — Two short blasts

A vessel planning to overtake another vessel at a safe distance is required to use two short blasts of sound signals. This signal communicates the intention of the overtaking vessel to indicate that it is moving to pass on the indicated side. The use of two short blasts is part of the standard sound signal conventions outlined in the Navigation Rules, which are designed to ensure clear communication between vessels, especially in situations where visibility may be limited or where multiple boats are operating in close proximity. Utilizing this specific sound signal helps prevent misunderstandings that could lead to collisions, as other vessels will recognize the overtaking intention and can then give way as appropriate. This practice emphasizes the importance of maintaining safety while navigating crowded or busy waterways.