Question 19 RVR01 - Master of Unlimited Tonnage

The Correct Answer is C. **Explanation for Option C (four to six seconds):** According to Rule 33(b) of the International Regulations for Preventing Collisions at Sea (COLREGs), which governs sound signals in restricted visibility: * The term "prolonged blast" means a blast of from **four to six seconds** duration. * The signal for a power-driven vessel making way through the water is one prolonged blast at intervals of not more than two minutes. * The signal for a power-driven vessel underway but stopped (not making way through the water) is two prolonged blasts separated by an interval of about two seconds, repeated at intervals of not more than two minutes. In both of these situations, the **duration of each individual prolonged blast** is defined as four to six seconds, making Option C the correct answer for both International and Inland rules (as U.S. Inland rules typically mirror the COLREG definitions for signal durations). **Explanation of Why Other Options are Incorrect:** * **A) about one second:** This duration defines a "short blast," not a "prolonged blast." Short blasts are used in maneuvering and warning signals (e.g., "I am altering my course to starboard"). * **B) two to four seconds:** This duration falls between the defined short blast and the defined prolonged blast and does not correspond to a standard specified duration for whistle signals in COLREGs. * **D) eight to ten seconds:** This duration is significantly longer than the standard definition for a prolonged blast (4–6 seconds). No standard mandatory signal in COLREGs requires a blast of this duration.