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 a tocolytic agent ? 
Select and explain. 
A. Prazosin, B. Ritodrine, C. Yohimbine, D. Propranolol
B: Ritodrine
Answer: B: Ritodrine 
Explanation: None