The correct answer is D) its low temperature causes frostbite or freezing. Liquefied petroleum gas, such as propane or butane, is stored under pressure as a liquid. When released, it rapidly expands and cools to very low temperatures, which can cause frostbite or freezing of exposed skin and other materials. This low temperature hazard is one of the principal dangers inherent in the handling and use of liquefied petroleum gases. The other answer choices are incorrect. Option A is incorrect because liquefied petroleum gas actually becomes lighter than air as it warms up and transitions to a gaseous state. Option B is incorrect because the reaction with seawater is not a principal danger. Option C is incorrect because the strong odor, while important for leak detection, is not a principal danger in itself.