When a vessel signals her distress by means of a gun or other explosive signal, the firing should be at intervals of approximately __________.

Correct Answer: Option A — 1 minute

COLREGS Annex IV defines approved distress signals, specifying that the firing of a gun or other explosive signals at intervals of approximately one minute indicates distress. This rhythmic auditory and visual signal draws immediate attention from vessels within hearing range during emergency situations at sea.