Green? Blue? Yellow? Which option represents signals in the given choices?

• A. No Signals
• B. Yard Limits
• C. Track Occupancy
• D. Signals

Answer: (D)

The main idea here is recognizing what term names the actual indications trains respond to. In railroad operations, signals are the devices or indications that tell a crew what they may do—proceed, slow down, or stop—often conveyed using color aspects like green, blue, or yellow. So the best choice is the term that directly refers to these indications: Signals. The other options describe related but distinct concepts: No Signals means there are no signal indications present, Yard Limits define a boundary with its own movement rules, and Track Occupancy indicates whether a train is currently on the track.