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
Which of the following is an oxytocin antagonist? 
Select and explain. 
A. Ritodrine, B. Atosiban, C. Isoxsuprine, D. Methergine
B: Atosiban
Answer: B: Atosiban 
Explanation: AtosibanREF: Danfoh's Obstetrics and Gynecology 10th Edition page 175-178, http://en.wikipedia.org/ wiki/Tocolytic See APPENDIX-64 for "TOCOLYTIC AGENTS"