If you spot an impaired driver, what should you do?

Answer: C — Call 911

Calling 911 is the appropriate action when you spot an impaired driver. This choice is correct because notifying law enforcement can help ensure the safety of the impaired driver, others on the road, and pedestrians. Impaired driving poses a significant risk of accidents, and trained officers can intervene in a way that is safe for everyone involved. In contrast, ignoring the situation can lead to potential road hazards and accidents, and following closely may escalate the scenario, possibly leading to dangerous driving conditions. Confronting the driver directly is also not advisable, as it can put you in harm's way and could provoke an aggressive response from the impaired individual. Thus, contacting authorities is the most responsible and safest approach.