6. When traveling on a highway divided into four traffic lanes, which vehicles are required to stop for a school bus that has stopped to unload children?

All vehicles traveling in the same direction as the school bus are required to stop when the bus is unloading children. This is to ensure the safety of the children as they exit the bus and cross the road.

However, the rules can vary depending on the state or country. In some places, vehicles traveling in the opposite direction on a divided highway are not required to stop. A divided highway is typically separated by a physical barrier or an intervening space. If the highway is not divided, or if there's no barrier, vehicles traveling in the opposite direction must also stop.

It's always important to know and follow the specific traffic laws in your area to ensure the safety of everyone on the road.