What part does NOT rotate when the engine is running and the clutch is depressed?

The input shaft does not rotate when the engine is running and the clutch is depressed. This situation occurs because the clutch separates the engine power from the transmission. When the clutch pedal is pressed, it disengages the clutch components, allowing the driver to shift gears without the engine's rotation affecting the transmission.

With the clutch depressed, the clutch plate and pressure plate are designed to disengage from the flywheel, which is directly connected to the engine. By doing this, power transfer between the engine and the transmission is interrupted, which allows the input shaft—connected to the transmission—to remain stationary while the engine continues to run. Therefore, in this scenario, the input shaft will not rotate as long as the clutch is fully engaged and depressed, separating it from the engine's movement.