Which device is used to indicate a hazard on or near the tracks?

Answer: C — red flag

A red flag is used to indicate a hazard on or near the tracks due to its high visibility and established significance in rail operations. The color red universally signals danger and alerts train crews and workers to proceed with caution. It serves as a visual warning that helps prevent accidents and ensures that personnel are aware of unsafe conditions. In rail environments, the clear and immediate recognition of a red flag is crucial for maintaining safety, as it effectively communicates urgency and the need for immediate attention to potential hazards. While caution signs and yellow lights serve important safety functions, they do not have the same immediate and direct impact as a red flag in signaling an imminent hazard. A safety cone is typically used in construction or road work contexts to direct traffic or indicate a temporary hazard, but it is not as effective on a railroad track where visibility from a distance is critical for safety. Thus, the red flag stands out as the most appropriate device for indicating hazards in proximity to the tracks.