When do you need to yield to emergency vehicles?

• Only when the emergency vehicle has its siren on
• Only when the emergency vehicle has its warning lights flashing
• When the emergency vehicle is using its siren and/or flashing warning lights
  Explanation:

  "You must always yield to emergency vehicles. Yield to police cars, fire engines, and ambulances when they sound a siren and/or flash warning lights. Pull over to the right edge of the roadway, clear of intersections, and stop until the emergency vehicle has passed. In heavy traffic, when you can't pull over, clear a path for the vehicle."
• Only when the emergency vehicle is a fire engine