This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
[{'content': "True about bell's curve is - \nSelect and explain. \nA. It skewed to the left, B. Has mean =1[?]0, C. Has standard deviation = 0[?]0, D. Has variance =1[?]0", 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Has variance =1.0 Standard normal curve (Bell curve or Gaussian distribution) has been explained in previous sessions.", 'role': 'assistant'}]