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

• Only the lanes going in the same direction as the school bus.
• Only the lanes going in the opposite direction of the school bus.
• No lanes need to stop.
• All four lanes must stop.
  Explanation:

  "On a four-lane undivided highway, all lanes—both in the same direction and the opposite direction of the school bus—must stop when the bus has its red lights flashing and stop sign extended."