Final answer:
The maximum legal blood alcohol content (BAC) for a driver of a commercial vehicle who is under 21 years old is 0%.
Step-by-step explanation:
The maximum legal blood alcohol content (BAC) for a driver of a commercial vehicle who is under 21 years old is 0% (Option A).
In most countries, including the United States, it is illegal for drivers under the legal drinking age of 21 to have any alcohol in their system while operating a commercial vehicle. This zero-tolerance policy is in place to ensure the safety of young drivers and other road users.
It is important for young drivers to understand the legal consequences and potential dangers of consuming alcohol before or while driving.