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 of Electroencephalogram have frequency of: \nSelect and explain. \nA. More than 14 cycles per second, B. Between 8 and 13 cycles per second, C. Less than 3.5 cycles per second, D. Between 4 and 7 cycles per second', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]