Based on the Fact That Stimulant Medications Have Been Used

Based on the fact that stimulant medications have been used effectively to treat ADHD, it is believed that the disorder may be caused by ____.

A) inadequate levels of acetylcholine in the central nervous system
B) an excess of serotonin in the central nervous system
C) an excess of norepinephrine in the central nervous system
D) inadequate neurotransmitters that affect signal flow to and from the frontal lobes