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
The hormone, which stimulates uterus contraction and lets down milk, is: 
Select and explain. 
A. Progesterone, B. Prolactin, C. Prostaglandin, D. Oxytocin
D: Oxytocin
Answer: D: Oxytocin 
Explanation: None