When a driver applies the brakes fully, then releases them once the wheels lock up, this technique is known as what?

Answer: B — Stab braking

The technique described in the question, where a driver applies the brakes fully and then releases them when the wheels lock up, is known as stab braking. This method is often used by drivers in situations where traction is compromised, such as on slippery surfaces, because it allows the driver to regain control of the vehicle. By stalling the brakes momentarily to prevent the wheels from skidding uncontrollably, drivers can better maintain steering control and avoid spinning out. Stab braking can be effective in large vehicles like trucks, where maintaining control is crucial to the safety of both the driver and others on the road. This technique contrasts with gradual braking, which is more about applying brakes slowly to reduce speed without the risk of wheel lock-up. It also differs from engine braking, where a driver relies on the engine's resistance to slow down the vehicle, and emergency braking, which refers to the urgent application of brakes to avoid a collision. Understanding stab braking is vital for drivers, especially in commercial trucking, as it helps mitigate the risk of accidents due to loss of control during braking.