What is the primary function of the master cylinder in a hydraulic system?

The primary function of the master cylinder in a hydraulic system is to apply hydraulic pressure to the wheel cylinders. When the brake pedal is pressed, the master cylinder generates pressure by forcing hydraulic fluid through the brake lines to the wheel cylinders. This pressure activates the cylinders, which then push the brake pads against the rotors to slow down or stop the vehicle. The master cylinder is essential for the effective operation of hydraulic braking systems, ensuring that the necessary force is applied consistently and reliably to slow down or stop the wheels.

In contrast, the other choices do not align with the master cylinder's role in the hydraulic braking system. Storing hydraulic fluid is a function of the fluid reservoir, not the master cylinder. Controlling the brake lights is an electrical function, typically involving a switch activated by the brake pedal. Regulating tire pressure is related to the tire's air pressure management system, not the hydraulic braking system.