At approximately what blood alcohol concentration (BAC) does impairment from alcohol typically begin to affect cognitive and motor functions in most adults?

• A. $0.30$ percent BAC
• B. $0.15$ percent BAC
• C. $0.08$ percent BAC
• D. $0.02$ percent BAC

Answer: (D)

Verified step by step guidance

1. Understand that Blood Alcohol Concentration (BAC) is a measure of the amount of alcohol present in a person's bloodstream, expressed as a percentage.
2. Recognize that impairment from alcohol begins when BAC reaches a level that affects cognitive and motor functions, such as reaction time, coordination, and judgment.
3. Review research findings and legal standards which indicate that even low levels of BAC can cause noticeable impairment in most adults.
4. Note that while higher BAC levels (e.g., 0.08% or above) are associated with significant impairment and legal intoxication, impairment typically begins at lower levels.
5. Conclude that impairment from alcohol generally starts at around 0.02% BAC, where subtle cognitive and motor function changes can be detected.