This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable Diseases, Subject name: Social & Preventive Medicine
[{'content': 'Formula shown is known as \nSelect and explain. \nA. Chandler index, B. Human development index, C. Life table analysis, D. Pearl index', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Pearl index', 'role': 'assistant'}]