BOTH INTERNATIONAL & INLAND You are underway in fog when you hear the following signal: one short blast, one prolonged blast and one short blast in succession. Which of the following would it be?

Correct Answer: Option D — A vessel at anchor

Under Inland Navigation Rules, for the condition where 'You are underway in fog when you hear the following signal: one short blast, one prolonged blast and one short blast in succession. Which of the following would it be', the correct requirement is: 'A vessel at anchor'. This standard ensures clear navigational intent and collision avoidance.