Final answer:
The drag link is part of a bus's steering system and is responsible for transferring motion from the steering gear to the wheels, allowing for directional changes.
Step-by-step explanation:
The component that belongs to the steering system of a bus is B. Drag Link. The drag link is part of the steering linkage mechanism and is essential for transferring the motion from the steering gear to the wheels, allowing for the change in direction of the vehicle. Components like the brake pedal are part of the braking system, the radiator is part of the cooling system, and the exhaust pipe is part of the exhaust system, which makes them unrelated to steering.