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: Gynaecology & Obstetrics
[{'content': 'A 28-year-old lady is suspected to have the polycystic ovarian disease. The sample for testing LH & FSH are best taken on the following days of the menstrual cycle \nSelect and explain. \nA. 10-Aug, B. 4-Jan, C. 13-15, D. 24-26', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Serum FSH concentrations vary signiﬁcantly across the cycle, hence serum FSH concentration is best obtained during the early follicular phase (cycle day 2–4)', 'role': 'assistant'}]