Under the IALA cardinal system, a mark with a quick light showing 9 flashes every 15 seconds indicates that the safest water is on the __________.

Correct Answer: Option A — west side of the mark

Under the IALA cardinal system, the number of flashes corresponds to the cardinal point. A quick light showing 9 flashes indicates a West cardinal mark. West cardinal marks signify that the safest water is located on the west side of the mark, away from the dangers the buoy is intended to protect.