What is the relay equipped with to align the coil and contact pins to the base?

The correct answer is indeed a keyway. In electrical relays, the alignment between the coil and contact pins is crucial for proper function. A keyway serves as a physical guide that ensures the coil and pins are positioned precisely when the relay is assembled onto its base. This alignment is essential for the relay to operate correctly, as misalignment could lead to poor electrical contact or even failure of the relay to actuate.

The other options do not fulfill the same function. For instance, a sensor might be used to monitor the operation of the relay, but it would not provide the necessary alignment. A locking mechanism could secure components in place, but it would not specifically address the alignment of the coil and pins. A circuit board is a platform for electrical connections and signal routing, but it does not contribute directly to aligning the internal components within the relay. Therefore, a keyway is specifically designed to address the need for alignment, making it the correct choice.