What must a conductor understand about signals?

Answer: C — They denote different conditions and responses expected

A conductor must understand that signals denote different conditions and the responses expected from them. This is essential in maintaining safety and efficiency in train operations. Signals provide vital information about track conditions, speed limits, and the status of other trains or track switches. By interpreting these signals correctly, a conductor can make informed decisions that affect the train's operation, such as whether to stop, proceed, or adjust speed. Knowing the meaning of various signals ensures that the conductor can respond appropriately to changing conditions on the track, which is crucial for preventing accidents and facilitating smooth train movements. The other considerations, such as train arrival times, crew shifts, and viewing signals as optional guidance, do not encapsulate the primary role signals play in a conductor's duties. Signals must be treated as mandatory and critical information for safe train operations.