This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthetic equipments, Subject name: Anaesthesia
What is mechanism of action of Curanium drugs as muscle relaxant? 
Select and explain. 
A. Persistently depolarizing at Neuromuscular junction, B. Act competitively on Ach receptors blocking post-synaptically, C. Repetitive stimulation of Ach receptors on muscle end plate, D. Inhibiting the calcium channel on presynaptic membrane
B: Act competitively on Ach receptors blocking post-synaptically
Answer: B: Act competitively on Ach receptors blocking post-synaptically 
Explanation: Candocuronium iodide is an aminosteroid neuromuscular-blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs. * Acts on Ach receptors competitively post-synaptically blocking them. * Potential adjunctive use in anaesthesia to facilitate endotracheal intubation & provide skeletal muscle relaxation. * Candocuronium demonstrated a sho duration and a rapid onset of action, with little or no ganglion blocking activity, and it was only slightly less potent than pancuronium REF : WILLEY 10 TH ED