What happens when the driver presses the brake pedal?

When the driver presses the brake pedal, it activates the brake system, initiating a series of mechanical processes that ultimately slow down or stop the vehicle. The brake pedal connects to either a hydraulic system or a mechanical linkage that causes the brake pads to press against the brake rotors (in disc brakes) or the brake shoes to press against the drum (in drum brakes). This creates friction, which is essential for effectively slowing down or halting the vehicle's motion.

The other options do not accurately describe the function of the brake pedal. For instance, pressing the brake pedal does not apply the accelerator or increase engine power; instead, it serves the opposite purpose by engaging the braking system to reduce speed. Therefore, the activation of the brake system directly correlates with the action of pressing the brake pedal, making it the correct interpretation of the question.