During adolescence, maturation of the lags behind maturation of the a. limbic system; frontal lobes b. brainstem; pituitary c. pituitary; brainstem d. frontal lobes; limbic system

During adolescence, maturation of the frontal lobes lags behind maturation of the limbic system. In humans the frontal lobe reaches full maturity around the late 20s, marking the cognitive maturity associated with adulthood. Changes in the parts of the brain continue into early adulthood. Because the prefrontal cortex is still developing, teenagers might rely on a part of the brain called the amygdala to make decisions and solve problems than adults do. The amygdala is associated with emotions, impulses, aggression and instinctive behavior. 

The answer would be sand and gravel