The correct answer is B) Use them only when you are aware of a ship or plane in the area. This is the correct answer because signal flares should be used judiciously when adrift in a liferaft to maximize their visibility and chance of being spotted by rescue aircraft or vessels. Flares should be conserved and only used when there is a reasonable chance of being seen, such as when you are aware of ships or planes in the vicinity. Using all the flares immediately or at a set interval is not the best practice, as it wastes the limited supply of flares and reduces the chances of being spotted when a rescue asset is actually in the area. The other options are incorrect because they do not align with the best practices for using signal flares in a survival situation. Expending all the flares at once or on a set schedule is not an efficient use of this important signaling equipment.