Which of these substances can impair driving ability?

Alcohol is well-known for its ability to impair driving ability. It affects cognitive functions, coordination, and reaction times, leading to an increased risk of accidents. While alcohol is legally consumed in many societies, its effects on the central nervous system can severely diminish a person's ability to operate a vehicle safely.

Caffeine, while it can affect alertness and energy levels, generally does not impair driving the same way alcohol does. In fact, moderate caffeine consumption can sometimes enhance alertness, although excessive amounts may lead to jitteriness or anxiety, which can be distracting. The choice indicating both caffeine and alcohol suggests a misunderstanding of the different impacts these substances have on driving ability. Therefore, identifying alcohol as the primary substance that impairs driving is accurate, while excluding caffeine from that classification helps clarify the risks associated with various substances.