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
Example of asymmetric mixed-onium chlorofumarate is: 
Select and explain. 
A. Rocuronium, B. Vecuronium, C. Gantacurium, D. Atracurium
C: Gantacurium
Answer: C: Gantacurium 
Explanation: Gantacurium represents a new class of nondepolarizing neuromuscular blockers called asymmetric mixed-onium chlorofumarates. Ref: Miller's anesthesia-7th ed , Chapter 29.