What are the signs of brake failure in a vehicle?

Answer: B — Signs include a drop in brake fluid level

When considering the signs of brake failure in a vehicle, the drop in brake fluid level is a significant indicator. Brake fluid is essential for the hydraulic braking system to function properly; if the level diminishes, it can result in reduced braking power or complete brake failure. Monitoring the brake fluid is crucial for the driver, as an unexpected drop can signal a leak or other issues within the braking system. While a sudden increase in speed might indicate a problem, it does not specifically relate to brake failure. A consistent brake pedal feel suggests that the brakes are functioning normally, which is contrary to the signs of failure. Unusual tire vibrations can indicate various issues with the vehicle, including tire problems or alignment issues, but they are not direct indicators of brake failure. Therefore, the drop in brake fluid level is the most direct and pertinent sign of potential brake failure.