To check your "blind spot," you must:

Answer: B — Look over your shoulder

To effectively check your blind spot, looking over your shoulder is essential. Blind spots are areas around your vehicle that are not visible through your mirrors, and relying solely on mirrors can be insufficient, especially for vehicles in adjacent lanes. By physically turning your head to look over your shoulder, you gain a direct view of these blind spots, which helps prevent accidents during lane changes or merges. While adjusting mirrors can help minimize blind spots and reduce the risk of missing vehicles in these areas, it does not completely eliminate the need to visually check directly by turning your head. Utilizing backup cameras can assist with reversing and monitoring what's directly behind you, but they do not help in checking side blind spots. Similarly, relying solely on side mirrors might still leave certain areas obscured due to the vehicle's design or position of other vehicles. Therefore, the action of looking over your shoulder provides a more comprehensive view and is crucial for safe driving practices in those scenarios.