This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Natural Methods, Barrier Methods, IUDs, OCPs, Subject name: Social & Preventive Medicine
[{'content': 'A woman has her shoest cycles of 26 days and longest cycle of 31 days. Calculate her unsafe period using Rhythm method ? \nSelect and explain. \nA. 21-Aug, B. 20-Sep, C. 19-Aug, D. 22-Aug', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Rhythm method: Aka calender method / safe period method / feile period method. Unsafe period = (Shoest cycle -18 days) to (longest cycle-10 days) Given shoest cycle = 26days; longest cycle = 31 days Unsafe period = to days = 8-21 days.', 'role': 'assistant'}]