Before pulling away from a bus stop, why must a bus driver thoroughly check the right-side external rearview mirror and blind-spot convex mirrors (下视镜/补盲镜)?

1. To check whether any late passengers, children, or non-motorized vehicles are trapped in the blind spot near the front or rear wheels
2. To inspect whether the vehicle's paint has faded during the stop
3. To ensure that oncoming vehicles in the opposite traffic lane are yielding
4. To verify that the bus advertising panels are facing the curb