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: Physiology
[{'content': 'Which of the following hormone is essential for breast milk ejection? \nSelect and explain. \nA. Oxytocin, B. Prolactin, C. Galactogen, D. GH', 'role': 'user'}, {'content': "Answer: A \nExplanation: Milk ejection occurs in response to a surge of oxytocin, which induces a contractile response in the smooth muscle surrounding the gland ductules. Oxytocin release is occasioned by stimuli of a visual, psychologic, or physical nature that prepare the mother for breast-feeding; whereas prolactin (PRL) release is limited to the suckling reflex arc. PRL is essential to milk production. Ref: Taylor R.N., Badell M.L. (2011). Chapter 16. The Endocrinology of Pregnancy. In D.G. Gardner, D. Shoback (Eds), Greenspan's Basic & Clinical Endocrinology, 9e.", 'role': 'assistant'}]