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 of cervical mucus depends on : \nSelect and explain. \nA. Estrogen, B. Progesterone, C. FSH, D. LH', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Estrogen', 'role': 'assistant'}]