Keeping the draft at or below the load line mark will insure that the vessel has adequate __________.

Correct Answer: Option D — reserve buoyancy

Load lines are established to ensure a vessel maintains sufficient reserve buoyancy, which is the volume of the watertight hull above the waterline. By keeping the draft at or below the load line mark, the vessel retains the necessary buoyancy to remain stable and seaworthy in adverse weather conditions.