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
Which of the following is the neuromuscular blocking agent with the shortest onset of action ? 
Select and explain. 
A. Mivacurium, B. Vecuronium, C. Rapacuronium, D. Succinylcholine
D: Succinylcholine
Answer: D: Succinylcholine 
Explanation: Fastest acting (shortest onset of action) muscle relaxant → Succinylcholine
Fastest acting non-depolarizing muscle relaxant → Rocuronium.