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
Mechanism of action of Tubocurarine is 
Select and explain. 
A. Cholinesterase inhibitor, B. Cause membrane depolarisation, C. Competitive antagonist of acetylcholine receptor, D. Inhibit opening of chloride channels
C: Competitive antagonist of acetylcholine receptor
Answer: C: Competitive antagonist of acetylcholine receptor 
Explanation: Tubocurarine is a non depolarizing muscle relaxant that competitively blocks action of Acetylcholine on its receptors.