This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': "Delta waves in EEG are 'seen in : \nSelect and explain. \nA. Deep sleep, B. REM sleep, C. Awake with eyes open, D. Awake with eyes closed", 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Deep sleep', 'role': 'assistant'}]