Final answer:
Differential braking is the method used by pilots to maintain directional control during a jammed rudder condition, as ailerons, anti-jam breakout mechanisms, and elevators are not as effective for this specific scenario.
Step-by-step explanation:
What helps the crew in directional control during a jammed rudder condition? The correct answer is a) Differential braking. In the event of a rudder jam, where the primary control surface for directional control is no longer available, pilots can use differential braking to steer the aircraft on the ground. Each main wheel can be braked independently allowing the aircraft to turn. While ailerons, anti-jam breakout mechanisms, and elevators serve important functions in flight control, they do not typically assist in directional control during a jammed rudder situation as efficiently as differential braking does.