Which statement is true concerning the drugs used to treat ADHD?

a. They generally produce a calming effect in only 25% of affected children.

b. Side effects of these medications have not been of great concern to physicians.

c. Low doses of these medications increase activity and arousal in children but not adults.

d. Most of these drugs affect dopamine, with the exception of new drug Strattera that works by affecting norepinephrine.

e. These drugs are impossible to abuse.