Long-term and short-term relaxation training are two common forms of treatment for individuals experiencing problematic levels of anxiety. Yet studies show that on average, regardless of which form of treatment one receives, symptoms of anxiety decrease to a normal level within the short-term-training time period. Thus, for most people the generally more expensive long-term training is unwarranted. Which one of the following, if true, most weakens the argument? ['Recipients of long-term training are much less likely than recipients of short-term training to have recurrences of problematic levels of anxiety.', 'A decrease in symptoms of anxiety often occurs even with no treatment or intervention by a mental health professional.', 'Short-term relaxation training conducted by a more experienced practitioner can be more expensive than long-term training conducted by a less experienced practitioner.', "The fact that an individual thinks that a treatment will reduce his or her anxiety tends, in and of itself, to reduce the individual's anxiety."]