Question 904 Rules of the Road

The correct answer is D) Sound not less than five short blasts. According to the navigation rules, if you do not understand the course or intention of an approaching vessel, both under international and inland rules, you should sound not less than five short blasts on the whistle. This signal indicates doubt or uncertainty about the other vessel's actions and is meant to alert the other vessel that you are unsure of their intentions, prompting them to take appropriate action. The other options are incorrect because they do not match the required signal for this situation. Sounding one short blast (A) or one prolonged blast (C) are used for different purposes, while sounding five prolonged blasts (B) would indicate an emergency situation, which is not the case here.