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: Social & Preventive Medicine
[{'content': 'The standard normal distribution : \nSelect and explain. \nA. Is skewed to the left, B. Has mean=1.0, C. Has standard detion=0.0, D. Has variance=1.0', 'role': 'user'}, {'content': "Answer: D \nExplanation: The standard detion in a standard normal curve is 1.0. The variance (SD2) is thus also one. Ref: Park's Textbook Of Preventive And Social Medicine By K. Park, 19th Edition, Page 702; Park's Textbook Of Preventive And Social Medicine By K. Park, 18th Edition, Page 647; Methods in Biostatistics: For Medical Students and Research Workers By BK Mahajan, 6th Edition, Page 68", 'role': 'assistant'}]