What is the legal blood alcohol content (BAC) for drivers under the age of 21?

Answer: A — 0.00%

Drivers under the age of 21 are not legally allowed to have any amount of alcohol in their system while operating a vehicle. This is because underage drinking is illegal and driving under the influence of alcohol is considered a serious offense. Option B, C, and D all have percentages associated with the legal BAC limit, but these are not the correct values for drivers under the age of 21. Option B is well above the legal limit for adult drivers, option C is the legal limit for adult drivers in most states, and option D is a common misconception but is not the legal limit for drivers under 21.