Adolescents may have difficulty curbing risky behaviors because the _________, the part of the brain responsible for reasoning, decision-making, and self-control, doesn't finish maturing until the emerging adult years.

The right answer is prefrontal cortex. This area of the brain is responsible for controlling impulses, decision making and reasoning. Mature between 18 and 25 years, and may even take longer to mature, which is why sometimes emerging adults perform risky actions or impulsive actions.

I hope my answer can help you.