Abner has been smoking marijuana regularly for 30 years when he participated in a study comparing cognitive performance between smokers and nonsmokers. after 28 days of abstinence from marijuana, he took the same tests given to nonsmokers
what effect did abstinence have on abner's cognitive abilities?
a) his cognitive performance was equivalent to the nonsmoker's
b) his cognitive performance was worse than the nonsmoker's.
c) his cognitive performance was better than the nonsmoker's.
d) his cognitive performance was still so impaired he couldn't complete the tests.