During the exhaust stroke of a 4 stroke engine, what occurs?

During the exhaust stroke of a four-stroke engine, the key focus is on the activity of the exhaust valve and the positioning of the intake valve. This stroke follows the power stroke and is crucial for removing the exhaust gases from the combustion chamber after fuel has been burned.

During this phase, the piston moves upward in the cylinder, which increases pressure and forces the exhaust gases out through the exhaust valve. The intake valve remains closed during this process to prevent exhaust gases from entering the intake track, ensuring that the combustion chamber is properly cleared of spent gases before the next intake stroke begins. Therefore, the correct answer describes this situation accurately.

In this context, the other options do not accurately represent the mechanics of the exhaust stroke. Proper valve operation is critical for the engine's efficiency during this phase, making it essential to have the exhaust valve open to facilitate gas expulsion while keeping the intake valve closed to maintain engine performance.