Final answer:
A person is legally considered 'Under the Influence of Alcohol' with a BAC of 0.08% or higher, a standard set by the National Minimum Drinking Age Act of 1984.
Step-by-step explanation:
A person 21 or more years of age is considered "Under the Influence of Alcohol" when a blood alcohol concentration (BAC) of 0.08% or more by alcohol weight is present in the blood. Legally, alcohol intoxication is defined as a BAC greater than 25-80 mg/dL or 0.025-0.080%, which can be measured by blood or breath testing. Factors such as age, sex, and health condition can affect an individual's BAC even when consuming the same amount of alcohol. The National Minimum Drinking Age Act of 1984 requires states to set the minimum drinking age to 21 to align with the federal standard for defining legal intoxication and addresses concerns regarding dru_nk driving and alcohol consumption by youths.