This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neurotic, Stress Related and Somatoform Disorders, Subject name: Psychiatry
[{'content': 'Which of the following is LEAST useful in treatment of OCD? \nSelect and explain. \nA. Clomipramine, B. SSRIs, C. Cognitive behavioral therapy, D. Systematic desensitization', 'role': 'user'}, {'content': 'Answer: D \nExplanation: SSRIs, Clomipramine and CBT are all first line treatment. Systematic desensitization is least effective of all.', 'role': 'assistant'}]