This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Osteoporosis, Sex Hormones and OCPs, Subject name: Pharmacology
[{'content': 'The estrogen that is used in most combined hormonal contraceptives is: \nSelect and explain. \nA. Clomiphene, B. Ethinyl estradiol, C. Estrone, D. Norgestrel', 'role': 'user'}, {'content': 'Answer: B \nExplanation: -Most commonly used estrogen in OCPs is ethinyl estradiol. -Most commonly used progesterone in OCPs is levonorgestrel.', 'role': 'assistant'}]