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: Pharmacology
True about atosiban is that it: 
Select and explain. 
A. Is an oxytocin receptor antagonist, B. Is an progesterone receptor antagonist, C. Is least effective in inhibiting preterm uterine contractions, D. Is a anti–tocolytic drug
A: Is an oxytocin receptor antagonist
Answer: A: Is an oxytocin receptor antagonist 
Explanation: None