When changing lanes, a driver should always do which of the following?

Answer: B — Check side mirrors and look over their shoulder

When changing lanes, checking side mirrors and looking over the shoulder is crucial for ensuring a safe maneuver. This practice allows the driver to be aware of their surroundings and check for any vehicles in adjacent lanes that may not be visible in the side or rearview mirrors. The side mirrors help provide a wider view of the lane beside the vehicle, while looking over the shoulder allows the driver to directly check the blind spot, which is an area that mirrors cannot adequately cover. This combination helps to ensure that no other vehicles are in the process of overtaking or are already in the lane the driver wishes to enter. Being vigilant in this manner helps prevent accidents that could occur from misjudgments about the presence of other vehicles, making it an essential part of safe driving practices.