What functional aspect does an optical unit's lens contribute to a traffic signal?

Answer: B — Visibility enhancement

The lens of an optical unit in a traffic signal is primarily designed to enhance visibility. This means that the lens plays a crucial role in directing and magnifying the light emitted from the signal. By effectively shaping and focusing the light, the lens ensures that the illuminated signal can be seen from a greater distance and in various lighting conditions, thus improving the overall visibility of the traffic signal for drivers and pedestrians. The manipulation of light through the lens allows for optimal performance of the signal, making it clearer and more noticeable, which is essential for safe traffic management. In contrast, sound amplification, weight reduction, and weather resistance are not functions associated with the lens of a traffic signal; these aspects relate to different components or materials used in traffic signal technology.