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: Anaesthesia
At the end of a balanced anaesthesia technique with non–depolarizing muscle relaxant, a patient recovered spontaneously from the effect of muscle relaxant without any reversal. Which is the most probable relaxant the patient had received – 
Select and explain. 
A. Pancuronium, B. Gallamine, C. Atracurium, D. Vecuronium
C: Atracurium
Answer: C: Atracurium 
Explanation: None