Answer:
Prefrontal cortex
Step-by-step explanation:
The brain grows significantly during adolescence. However, the front part of the brain, called the prefrontal cortex, is remodeled last, as the major changes happen in the back part of it.
The prefrontal cortex is the part of the brain responsible for decisions making, solving problems, controlling impulses and thinking about consequences of actions.
Since this part of the brain is still developing in adolescence, teenager rely on the amygdala part of their brains to make decisions. The amygdala is associated with high emotions, impulsiveness, aggression and instinctive behavior. This is why they engage in dangerous behaviors, their still-developing brains tell them to do so.