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
[{'content': 'Progesterone has how many carbons \nSelect and explain. \nA. 18, B. 19, C. 20, D. 21', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Progesterone (P4)C21H30O2is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the major progestogen in the body. Progesterone is also a crucial metabolic intermediate in the production of other endogenous steroids, including the sex hormones and the coicosteroids, and plays an impoant role in brain function as a neurosteroid.Ref: Ganong&;s review of medical physiology; 24th edition; page no:-409', 'role': 'assistant'}]