What must you do when approaching a school bus stopped on a two-lane pavement, its red warning lights flashing, and its stop arm extended?

Answer: C — Stop and yield to pedestrians 20 ft away

When approaching a school bus that is stopped on a two-lane pavement with its red warning lights flashing and its stop arm extended, the correct action to take is to stop and yield to pedestrians who are 20 feet away in either direction. This is an important safety measure to ensure the safety of children who may be crossing the road to board or exit the school bus. It is crucial to follow this rule to prevent any potential accidents and ensure the well-being of pedestrians, especially children who are getting on or off the school bus.