What is the typical legal BAC limit for drivers aged 21 and over in most states?

• A. 0.05 percent BAC
• B. 0.00 percent BAC
• C. 0.08 percent BAC
• D. 0.10 percent BAC

Answer: (C)

For adult drivers, the law uses a per se limit: if your BAC is at or above 0.08%, you’re considered legally impaired to drive. This 0.08% threshold is the standard adopted by most states for drivers aged 21 and over, making it illegal to operate a vehicle once that level is reached or exceeded, based on a breath or blood test.

Impairment can begin at lower levels, and some situations or categories (like commercial drivers or underage drivers) use different limits, but 0.08% is the typical standard for adults 21 and over. The other options are less representative of the common rule: 0.05% is used in some contexts or states, 0.00% would imply zero tolerance that isn’t the general rule for adults, and 0.10% is higher than the standard in most places.