What does the word sullen mean in this sentence?

Consider the text and its central idea. informational text: one privilege that many teens look forward to is the ability to earn a driver’s license. driver’s licensing requirements are not the same in every state. in some states, young people can be fully licensed before their sixteenth birthday. in other states, the privilege to drive has some restrictions until the driver is eighteen years old. in every state, driver education is a required step in earning a license. students might earn a permit, or provisional license, and spend six months to a year driving with an adult in the car. since states are very different based on population, development, and roadways, the laws are different, too. central idea: states makes different laws about licensing drivers with some similar requirements. what supporting detail is most important to include in a summary of this text? teens get excited about learning to drive. in some states, kids can get their license on their birthday. some states are heavily populated, with dangerous roads to navigate. every state includes driver education as part of licensing requirements.