Upon the approach of an official emergency vehicle, what action should a motorist take?

Answer: B — Pull over and stop

When an official emergency vehicle approaches, it is crucial for motorists to follow the correct protocol in order to ensure the safety of both themselves and the emergency responders. Option A, blazing headlights, would be incorrect as this action does not give the emergency vehicle a clear path and could potentially blind the driver. Option C, increasing speed, would also be incorrect as this can cause confusion and put both parties in danger. Option D, moving to the left lane, could impede the emergency vehicle's designated lane and hinder their ability to quickly reach their destination. The only safe and appropriate action for a motorist to take upon the approach of an official emergency vehicle is to pull over and stop, allowing the emergency vehicle to pass.