Which vehicles are required to stop at a stop sign?

Answer: B — Vehicles 2 and 3

The correct answer indicates that vehicles 2 and 3 are required to stop at a stop sign. In the context of roadway rules, the requirement to stop at a stop sign applies to all vehicles approaching that intersection. Stop signs are placed at intersections to control traffic flow and ensure safety by requiring vehicles to come to a complete stop before proceeding. While the provided answer identifies specific vehicles that must stop, it's essential to recognize that all vehicles present at the intersection are generally required to comply with the stop sign rule. The expectation is to assess the right-of-way and ensure safe navigation through the intersection. This principle emphasizes the importance of defensive driving and situational awareness, as failing to stop can lead to accidents and violations of traffic laws. Ensuring all vehicles stop helps maintain safety for all road users, including pedestrians.