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': 'The Standard Days Method (SDM) advices on avoiding unprotected sexual intercourse: \nSelect and explain. \nA. From day 3 to 13 of menstrual cycle., B. From day 8 to 28 of menstrual cycle, C. From day 8 to 21 of menstrual cycle, D. From day 3 to 19 of menstrual cycle', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Standard days method: It is for the women having their cycle lengths between 26-31 days. Have their feile days between 8 to 19 days of cycle. Hence, SDM advices on avoiding unprotected sexual intercourse during these days of menstrual cycle.', 'role': 'assistant'}]