Which lanes should stop for a school bus on a two-lane undivided highway?

• Only the lane in which the school bus is driving.
• Only the lane opposite to the school bus.
• Both lanes must stop.
  Explanation:

  "On a two-lane undivided highway, traffic in both directions must stop when a school bus has its red lights flashing and stop sign extended for the safety of children crossing the road to board or exit the bus."
• No lane needs to stop.