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: Physiology
[{'content': 'Blood levels of progesterone are highest during _____. \nSelect and explain. \nA. The follicular phase of the ovarian cycle, B. The luteal phase of the ovarian cycle, C. Ovulation, D. Menstruation', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Progesterone concentration in blood is highest following the surge of LH (leuteinizing hormone) following ovulation.\nDuring ovulation, estrogen surges due to positive feedback during the follicular phase.\nDuring menstruation, there are sharp declines in estrogen and progesterone due to reduced secretion of LH and FSH.', 'role': 'assistant'}]