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: Pharmacology
[{'content': 'All of the following are natural estrogens except ? \nSelect and explain. \nA. Estradial, B. Ethinylestradiol, C. Estriol, D. Estrone', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Ethinylestradiol o Estradial, estrone and estrial, all three are found in blood, but estradiol is the most potent estrogen.", 'role': 'assistant'}]