This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Physiology
Source of progesterone during normal menstrual cycle 
Select and explain. 
A. Corpus luteum, B. Stroma, C. Surface epithelium of ovary, D. Seoli cells
A: Corpus luteum
Answer: A: Corpus luteum 
Explanation: Progesterone is a steroid sex hormone that is the principal progestational agent; it plays a major pa in the menstrual cycle. During the maturation of the secondary oocyte (ovum), estrogen, the principal female sex hormone, is produced at a high rate. At ovulation estrogen production is sharply reduced, and the ovary then creates within itself a special endocrine structure called the corpus luteum whose sole function is to produce progesterone.Ref: Ganong&;s review of medical physiology; 24th edition; page no:-401