Which of the following statements is true about liquefied petroleum gas (LPG)?

The statement that liquefied petroleum gas (LPG) can remain liquid under pressure is true and highlights one of the essential characteristics of LPG. When subjected to high pressure, LPG exists in a liquid state, which allows it to be easily transported and stored in cylinders and tanks. This property is fundamental for its effective use in various applications, including heating, cooking, and automotive fuel.

LPG is typically composed mainly of propane and butane, not methane, which makes the first statement inaccurate. When burned, LPG does produce emissions, although they are generally lower compared to some other fossil fuels; thus, it is not correct to say it produces no emissions at all. Lastly, regarding efficiency, LPG is generally considered to be more efficient than natural gas in terms of energy content provided per unit volume, making the statement about its efficiency incorrect as well. Thus, the correct understanding revolves around the ability of LPG to remain liquid under pressure, which is a key feature of this fuel type.