The correct answer is: A. Formed by the longitudinal axis of the aircraft and the direction of movement of the nose gear.
Castor angle is the angle between the longitudinal axis of the aircraft and the direction of movement of the nose gear. It is used to maintain directional stability during taxiing and takeoff.
Option B is the definition of the windward drift angle.
Option C is the definition of the crosswind component.
Option D is the definition of the dihedral angle.