By what age must you have held your learner's permit to obtain a full license in Tennessee?

Answer: B — 18 years old

In Tennessee, the law requires that an individual must hold their learner's permit for at least 6 months before they can apply for a full unrestricted license. While applicants can be 16 years old or older to have a learner's permit, they must also meet additional requirements, such as completing a driver education course, turning 18, or holding the permit for the requisite duration. Therefore, obtaining a full license is contingent on having held that learner's permit until at least 18 years of age, ensuring that drivers have gained sufficient experience behind the wheel.