It is illegal for a person 21 years of age or older to drive with a blood alcohol concentration (BAC) of what percentage or higher?

The correct answer is based on established laws regarding driving under the influence of alcohol. For individuals 21 years of age or older, the legal limit for blood alcohol concentration (BAC) is set at eight hundredths (0.08) of one percent. This standard is widely recognized and enforced across the United States and serves as a critical threshold in determining whether a driver is considered impaired.

When a person's BAC reaches or exceeds this limit, they are subject to legal penalties, which may include fines, license suspension, or even imprisonment depending on the circumstances and previous offenses. This standardized limit is grounded in research that indicates significant impairment in driving abilities, coordination, and reaction times at this level of alcohol consumption.

Other BAC levels mentioned, such as five hundredths (0.05), one tenth (0.10), and eleven hundredths (0.11), do not represent the established legal threshold for driving impairment in most jurisdictions. While different states may have varied laws concerning these lower or higher limits, the universally accepted legal limit for those aged 21 and older remains 0.08 percent. Understanding this limit is crucial for safe driving practices and legal compliance.