Upon approaching a stationary authorized emergency vehicle or highway maintenance vehicle and when these vehicles are displaying alternatively flashing lights, a person who drives an approaching vehicle shall:

Answer: C — Proceed with due caution

Upon approaching a stationary authorized emergency vehicle or highway maintenance vehicle displaying alternatively flashing lights, a driver should proceed with due caution. This means reducing your speed, being prepared to stop if necessary, and being alert for any possible obstacles or hazards on the road ahead. It is essential to ensure the safety of the emergency responders or highway workers and to prevent any accidents that may occur due to sudden movements or distractions. Therefore, option C is the correct choice as it reflects the appropriate way to handle this situation.