This question seems to assume you are in a power-driven vessel with no other encumberances. If you were previously towing or RAM, suddenly becoming a NUC would not necessitate a change in fog signal.
Deck
Rules of the Road: BOTH INTERNATIONAL & INLAND If underway in low visibility and sounding fog signa...
Discussing this exam question.
It's only a towing vessel or ram if stated so
Rule 35b states " a power-driven vessel underway but stopped and making no way through the water shell sound at intervals of not more than 2 minutes to prolong last in succession with an interval of about two seconds between them"
It`s a vessel not under command, correct answer
The correct answer is (D) NOT (B).
Correction B not D, due to the exceptional circumstance in accordance Rule 3(f), therefore Rule 35(c) applies and you sound one prolonged 2 short not to exceed 2 min intervals.
Rule 35 (d)