To check blind spots while driving, the driver must:

Answer: D — Turn your head and look over your shoulder

To effectively check blind spots while driving, the most reliable method is to turn your head and look over your shoulder. This action allows the driver to see areas that are not covered by mirrors, ensuring a comprehensive view of the surroundings. When a driver only relies on mirrors—such as the rearview and side mirrors—their perspective may still miss vehicles or objects that are in the blind spots, which are typically located just behind the driver's line of sight. While checking mirrors is important, it does not provide the complete spatial awareness needed to merge or change lanes safely. Turning your head allows you to physically look into the areas that could potentially contain another vehicle or obstacle, which enhances safety and reduces the risk of collisions. Thus, this action is crucial for responsible driving practices.