What action confirms the effectiveness of the parking brake during a final test?

Answer: B — Tugging against the parking brakes in low gear

The action that confirms the effectiveness of the parking brake during a final test is tugging against the parking brakes in low gear. This method tests the holding power of the parking brake under a load, allowing the driver to assess whether the brake can keep the vehicle stationary while it is in gear. By applying torque through the drive train in low gear, you effectively evaluate the strength and reliability of the parking brake mechanism, confirming it can secure the vehicle on an incline or against any potential rolling movement. Using this approach provides a practical evaluation of the parking brake's function, ensuring it can perform its intended purpose safely. Other actions, like moving the vehicle at high speed or pressing the brake pedal quickly, do not specifically address the parking brake's capability to hold the vehicle in place when needed, and releasing the foot throttle doesn't engage the parking brake system's effectiveness.