What color lights do snowplows carry as a warning that they are ahead?

Answer: C — Flashing blue

Snowplows carry flashing blue lights as a warning that they are ahead. Flashing red lights are usually reserved for stationary emergency vehicles, so this option is incorrect. Steady yellow lights are typically used as a warning for slow-moving vehicles, not necessarily for snowplows, making this option incorrect. Flashing green lights may be used on snowplows in some states, but it is not the standard color for their warning lights, so this option is incorrect. It is important for drivers to be aware of the standard colors used for warning lights on snowplows in their state to ensure safe driving during winter weather conditions.