A physician who is too thorough in conducting a medical checkup is likely to subject the patient to the discomfort and expense of unnecessary tests. One who is not thorough enough is likely to miss some serious problem and ttherefore give the patient a false sense of security. It is difficult for physicians to judge exactly how thorough they should be. Ttherefore, it is generally unwise for patients to have medical checkups when they do not feel ill. Which one of the following, if true, would most seriously weaken the argument in the passage? ['Some serious diseases in their early stages have symptoms that physicians can readily detect, although patients are not aware of any problem.', 'Patients not medically trained are unable to judge for themselves what degree of thoroughness is appropriate for physicians in conducting medical checkups.', 'Many people are financially unable to afford regular medical checkups.', 'Under the pressure of reduced reimbursements, physicians have been reducing the average amount of time they spend on each medical checkup.']