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: Psychiatry
[{'content': 'IQ is - \nSelect and explain. \nA. Mental age / chronological age x 100, B. Chronological age / mental age x 100, C. Mental age + chronological age x 100, D. Mental age - chronological age x 100', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]