BOTH INTERNATIONAL & INLAND Fog signals, required under the Rules for vessels underway, shall be sounded __________.

Correct Answer: Option B — at intervals of not more than two minutes

Under Inland Navigation Rules, for the condition where 'Fog signals, required under the Rules for vessels underway, shall be sounded', the correct requirement is: 'at intervals of not more than two minutes'. This standard ensures clear navigational intent and collision avoidance.