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': 'Pearl Index of SAHEIL \nSelect and explain. \nA. 2/HWY, B. 14/HWY, C. 0.1/HWY, D. 9/HWY', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]