Therapist: In a recent study, researchers measured how quickly 60 different psychological problems waned as a large, diverse sample of people underwent weekly behavioral therapy sessions. About 75 percent of the 60 problems consistently cleared up within 50 weeks of therapy. This shows that 50 weekly behavioral therapy sessions are all that most people need.

Question: The therapist's argument is logically most vulnerable to criticism on the grounds that it
Options:
A. takes for granted that there are no psychological problems that usually take significantly longer to clear up than the 60 psychological problems studied
B. fails to address the possibility that any given one of the 60 psychological problems studied might afflict most people
C. takes for granted that no one suffers from more than one of the 60 psychological problems studied
D. fails to address the possibility that some forms of therapy have never been proven to be effective as treatments for psychological problems
E. takes for granted that the sample of people studied did not have significantly more psychological problems, on average, than the population as a whole
Answer: "B"