What is produced during the power (combustion) stroke?

During the power (combustion) stroke, the ignition of the compressed air-fuel mixture occurs, resulting in a rapid expansion of gases. This expansion generates a significant amount of pressure that forces the piston downward in the cylinder, producing power to turn the crankshaft. The entire process is essential for the engine's operation, as it converts the chemical energy from the fuel into mechanical energy that ultimately drives the engine.

In the context of the other options, it’s important to note that the piston moving upward to compress the mixture pertains to the compression stroke, not the power stroke. The exit of exhaust gases from the cylinder occurs during the exhaust stroke, following the power stroke. Lastly, mixing fuel with air takes place during the intake stroke, before either compression or combustion occurs. Thus, focusing on the events specific to the power stroke, the ignition and subsequent forced descent of the piston are foundational to understanding engine operation.