Caster angle affects how the steering axis tilts from vertical when viewed from the side of the vehicle.
A positive caster angle provides straight-line stability but makes steering effort heavier.
If the positive caster is excessive, it not only increases the steering effort but also transmits more road shocks directly to the steering wheel.
This means the driver feels bumps and vibrations more strongly through the steering.
The front wheel itself absorbs shocks through suspension, but the steering mechanism passes these to the driver’s hands.
Passenger seat and rear axle are not directly affected by caster angle in this context.
Therefore, the correct answer is steering.