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: Biochemistry
[{'content': 'Which of the following contains as aromatic a ring? \nSelect and explain. \nA. Estradiol, B. Testosterone, C. Aldosterone, D. Coisol', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Estradiol is the 17-beta-isomer of estradiol, an aromatized C18 steroid with hydroxyl group at 3-beta- and 17-beta-position.Ref: DM Vasudevan, 7th edition, page no: 669', 'role': 'assistant'}]