What type of signal would require a conductor to reduce speed?

Answer: B — Approach signal

A signal that indicates a conductor should reduce speed is an approach signal. This type of signal typically advises the train operator that they need to prepare for the possibility of a more restrictive signal ahead, such as a stop signal or a slow signal. By reducing speed, the conductor can ensure that the train is operating safely and in compliance with the signaling system, allowing them to respond appropriately to changing conditions on the track. The approach signal serves an important role in maintaining safety during transit, as it anticipates upcoming changes in the signaling system that may require a complete stop or further speed reduction. Thus, when a conductor sees this signal, their training dictates that they take action to slow down in preparation for whatever may come next.