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 one of the following skeletal muscle relaxants causes pain on injection ? 
Select and explain. 
A. Succinyl choline, B. Vecuronium, C. Rocuronium, D. Pancuronium
C: Rocuronium
Answer: C: Rocuronium 
Explanation: None