During which stroke does the combustion of gas occur?

The correct answer is the Power Stroke, which is the phase in a four-stroke engine where combustion of the fuel-air mixture occurs. During this stroke, the engine's piston is forced down the cylinder as the explosion of combustion gases occurs, creating the power needed to turn the crankshaft and ultimately drive the vehicle.

In the context of an engine's operation, the Power Stroke is preceded by the Compression Stroke, where the fuel-air mixture is compressed, making it more volatile. After the Power Stroke, the Exhaust Stroke follows, during which the spent gases are expelled from the cylinder, preparing for the next cycle. The Intake Stroke, on the other hand, is the phase where the engine draws in a new fuel-air mixture, and thus there is no combustion during this stroke.

Understanding this sequence and the role of the Power Stroke is crucial for comprehending how small engines function effectively, and it reflects the basic principles of engine cycles.