How does the exhaust valve operate during the exhaust stroke?

During the exhaust stroke of an internal combustion engine, the primary function of the exhaust valve is to release combustion gases from the cylinder after the power stroke. The camshaft plays a crucial role in this process. It is designed to rotate and push on the rocker arm, which in turn opens the exhaust valve at the appropriate time during the exhaust stroke.

The correct answer emphasizes the active role of the camshaft in facilitating valve movement. When the piston moves upwards in the cylinder during the exhaust stroke, it creates a low-pressure area that helps pull the exhaust gases out. However, it is the camshaft's precise timing and mechanical action that actually opens the exhaust valve, allowing the gases to escape. This controlled opening is essential for proper engine function and to ensure that the exhaust gases leave the cylinder efficiently, thus allowing for a fresh charge of air and fuel to enter during the intake stroke that follows.

Other options suggest alternate mechanisms which do not accurately reflect the established operation of the valve during this phase of the cycle. The involvement of the camshaft ensures that the timing of the exhaust valve opening is synchronized with the engine’s operating cycle, which is critical for maximizing efficiency and power.