The correct answer is D) Life preservers are designed to turn an unconscious person's face clear of the water. This is correct because life preservers (Type I personal flotation devices) are specifically designed to turn an unconscious person from a face-down position in the water to a vertical or slightly backward position, keeping their face out of the water. This is a critical safety feature, as it prevents drowning of an unconscious individual. The other answer choices are incorrect - A) is false as life preservers do not need to be worn in a specific orientation, B) is false as lightly stained or faded life preservers can still function properly, and C) is false as buoyant vests cannot be substituted for approved life preservers on vessels.