Determining the Nature of the Relationship Between Cognitive Impairment and the Prolonged

Multiple Choice

Determining the nature of the relationship between cognitive impairment and the prolonged use of amphetamines can be difficult because

A) amphetamines don't actually cause brain damage.
B) people taking amphetamines refuse to be tested.
C) researchers cannot determine the cause-and-effect relationship between cognitive impairment and amphetamine use from correlational data.
D) there are no known long term risks associated with these drugs.