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
Sleep disturbances are diagnosed by - 
Select and explain. 
A. Polysomnography, B. Oximetry, C. Echocardiography, D. Orthography
A: Polysomnography
Answer: A: Polysomnography 
Explanation: 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.