When fighting a fire on a bulkhead using a portable carbon dioxide extinguisher, the stream should be directed at the __________.

Correct Answer: Option B — base of the flames, moving the horn from side to side, following the flames upward as they diminish

Standard marine firefighting technique requires sweeping the discharge horn from side to side at the base of the fire. As the flames diminish, follow them upward to sweep away remaining vapors, ensuring complete extinguishment and preventing flash-back.