The correct answer is D) is effective if used promptly on an oil fire. Carbon dioxide is an effective fire extinguishing agent for oil-based fires because it works by displacing oxygen, which is necessary for combustion. When used promptly, the carbon dioxide can smother the fire and cut off the oxygen supply, effectively extinguishing the flames. This makes carbon dioxide a particularly suitable choice for fighting oil-based fires, as opposed to water which would not be as effective. The other answer choices are incorrect. Option A is incorrect because carbon dioxide does not have a greater cooling effect than water. Option B is incorrect because carbon dioxide is actually heavier than air, not lighter. Option C is incorrect because carbon dioxide can be harmful to cargo and crew if used in confined spaces without proper ventilation.