Which of the following, if true of doctors who make house calls, most seriously weakens the argument? A. They are more likely than are doctors who do not make house calls to believe that a doctor's bedside manner is an important part of medical treatment. B. They see their patients more frequently than do doctors who do not make house calls and so acquire more information about the patients' conditions. C. They tend to have fewer years of experience at practicing medicine than do doctors who do not make house calls. D. They perform all the same types of treatment as doctors who do not make house calls. E. They are not charged any less for malpractice insurance than are doctors who do not make house calls.