You are approaching another vessel on your starboard bow that sounds five short blasts. What should you do?

Answer: C — Make a big change of course and reduce speed if necessary

When encountering another vessel that is approaching on your starboard bow and sounds five short blasts, the proper response is to make a significant course change and reduce speed if necessary. This action aligns with the intent of the signaling vessel, which is likely indicating uncertainty about your intentions or warning you of a possible collision situation. By making a big course alteration, you effectively communicate your intention to avoid collision and ensure that you are moving in a safe manner. Additionally, reducing speed helps to give both vessels more time to react to any changes in the situation, making it clearer and safer for everyone involved. Maintaining your course and speed can lead to a dangerous situation, as the vessel signaling may be attempting to alert you that your actions could result in a collision. A small course change might not be sufficient to prevent an incident, especially if there is confusion about your intentions and the other vessel's course. Sounding a warning signal does not address the need to avoid a collision actively and may increase uncertainty without making substantial changes to your maneuvering. Thus, making a big course change while reducing speed is the preferred and safest course of action in this scenario.