This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sleep Disorders, Subject name: Psychiatry
[{'content': 'Sleep disturbances are diagnosed by - \nSelect and explain. \nA. Polysomnography, B. Oximetry, C. Echocardiography, D. Orthography', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Polysomnography * Polysomnography is an essential tool in the formulation of diagnoses for sleep disorder patients and in the enhancement of our understanding of normal sleep.", 'role': 'assistant'}]