What indicates that a trailer has an Anti-lock Braking System (ABS)?

Answer: B — Presence of wheel speed sensors

The presence of wheel speed sensors is an important indicator that a trailer is equipped with an Anti-lock Braking System (ABS). These sensors are crucial components of the ABS, as they monitor the speed of each wheel and provide the system with the necessary data to prevent wheel lock-up during braking. When the ABS is engaged, it adjusts brake pressure to maintain traction and enhance steering control, which is vital for safe maneuvering, especially on slippery surfaces. While a visible ABS warning light during inspection does help confirm the system's operational status, it does not initially indicate the presence of ABS itself; rather, it serves as a diagnostic tool to alert the driver to potential issues. Similarly, while manufacturers may use labels to denote ABS, the actual functioning of the system relies fundamentally on the presence of the wheel speed sensors. Lastly, testing for ABS would not be an effective way to identify its existence, as it is not feasible to discern the system's presence without examining its components directly.