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: Gynaecology & Obstetrics
[{'content': 'Ferning pattern of mucus under influence of: March 2013 \nSelect and explain. \nA. Progesterone, B. Testosterone, C. Estrogen, D. Prostaglandins', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C i.e. Estrogen', 'role': 'assistant'}]