What is the working fluid in a gasoline engine?

The correct answer highlights the role of combustion gases and an air mixture as the working fluid in a gasoline engine. In a gasoline engine, fuel is mixed with air and drawn into the cylinder. When the mixture is ignited by a spark, it combusts, creating high-pressure gases that expand and push the piston down. This expansion of gases is harnessed to convert chemical energy from the fuel into mechanical energy to drive the engine.

Additionally, gasoline engines rely on the efficiency of this mixture and the resulting pressure to produce power. The air-fuel mixture is crucial for the combustion process, which distinguishes it from other working fluids like water and steam, which are used in different types of engines or power systems, such as steam engines or turbines. The effectiveness of combustion gases as the working fluid is essential to the operation of gasoline engines, making this choice the best answer.