Critical Reasoning

In an experiment involving addicted cigarette smokers, each subject
was unknowingly administered either the new drug Nico-Gone or a
placebo. One year later, less than a third of the subjects who were
administered Nico-Gone had resumed smoking, compared with
about two thirds of the subjects who were administered a placebo.
These reports confirm that Nico-Gone is effective in curing addiction
to cigarette smoking.
Which of the following, if true, most strongly supports the conclusion
above?
A. One year after the experiment, the percentage of the experiment's
subjects who were cigarette smokers was less than the
percentage of the general population who were smokers.
B. Other reliable studies indicate that cigarette smokers often
falsely inform others that they are not smokers.
C. During the year following the experiment, cigarettes were
readily available to all of the subjects.
D. One year after the experiment, the total number of subjects
who were cigarette smokers was less than the number who
were smokers one year prior to the experiment.
E. During the year following the experiment, some of the subjects
received other treatment to help them avoid cigarette smoking.

OA:: [spoiler] AFTER DISCUSSION[/spoiler]