The Fact That Stimulant Drugs Are Often Effective in Calming

The fact that stimulant drugs are often effective in calming children diagnosed with ADHD suggests that this disorder may involve:

A) a chronic understimulation in the child's nervous system
B) problems in the brain pathways that regulate attachment behavior
C) a hypersensitivity to the presence of sugar in the bloodstream
D) too much activity in the parts of the brain that control behavior