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
The type of estrogen found in highest concentration in adult female is 
Select and explain. 
A. Estrone, B. Estriol, C. Estradiol, D. None
C: Estradiol
Answer: C: Estradiol 
Explanation: b-Estradiol; 17b-estradiol; the most potent naturally occurring estrogen in mammals, formed by the ovary, placenta, testis, and possibly the adrenal coex; therapeutic indications for estradiol are those typical of an estrogen. a-Estradiol (17a-estradiol), exhibits considerably less biologic activity.Ref: Ganong&;s review of medical physiology; 24th edition; page no: 406