Alex is 17 and has successfully held his intermediate license for 12 months with no violations. He goes to the DMV to apply for his full, unrestricted license but is told he is not yet eligible. Which of the following is the most likely reason?

1. He forgot to bring his driver education completion certificate.
2. He was required to have a supervising driver accompany him to the DMV.
3. His state requires drivers to be at least 18 years old for a full license.
4. He needed to have held the intermediate license for 18 months, not 12.