What equipment is required for warning vehicles that are parked?

Answer: B — Three reflective triangles, six fuses, or three liquid-burning flares

The requirement for warning vehicles that are parked focuses on safety and visibility for other drivers. Three reflective triangles or, as alternatives, six fuses or three liquid-burning flares are mandated to provide adequate warning to approaching traffic, especially in low visibility conditions such as at night or during inclement weather. Reflective triangles are particularly effective as they can be easily seen from a distance and can be set up in a manner that directs oncoming drivers to the presence of a stopped vehicle. The other options do not meet the necessary requirements for ensuring that a parked vehicle is adequately warned. While cones and flares can enhance safety, they might not provide the comprehensive warning that three reflective triangles or their alternatives can. A single red flag combined with two flares may not provide sufficient warning either, as it lacks the stability and visibility that multiple triangles present. Lastly, having only one triangle and one flare does not fulfill the standard requirements for signaling a stopped vehicle effectively.