Which of the following substances has been shown to impair one's ability to drive?

The correct choice highlights that both alcohol and marijuana can significantly impair a person's ability to drive safely. Research has consistently shown that alcohol affects motor skills, reaction times, and decision-making, leading to a higher risk of accidents. Similarly, marijuana has been found to impair various cognitive functions, including attention, complex problem-solving, and motor coordination, which are critical for safe driving.

When it comes to alcohol, it can lead to slower reaction times and poor judgment, making it one of the primary substances associated with impaired driving. On the other hand, marijuana can create difficulties in maintaining focus and accurately processing information, thus affecting driving performance.

Recognizing the impairment caused by both substances reinforces the importance of responsible behavior regarding substance use, emphasizing the necessity for individuals to be aware of how different substances can impact their driving abilities. This understanding is crucial for promoting roadway safety and reducing the incidence of DUI-related incidents.