How does the power brake assist the driver? a. It uses an outside source of force to increase the driver's pedal effort. b. It recycles the brake fluid to increase the driver's pedal effort. c. It uses a long lever to increase the driver's pedal effort. d. It uses the pushrod length to increase the dkiver's pedal effort.

The correct answer is a. It uses an outside source of force to increase the driver's pedal effort.<br /><br />Power brake systems use an outside source of force, typically a hydraulic pump driven by the engine, to increase the driver's pedal effort. This hydraulic pressure assists the driver in applying the brakes, making it easier to stop the vehicle.