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: Microbiology
Clostridium botulinum toxin mode of action is by: March 2012 
Select and explain. 
A. Presynaptic block, B. Postsvnaptic block, C. Competitive inhibition of acetylcholine, D. Destruction of acetylcholine
A: Presynaptic block
Answer: A: Presynaptic block 
Explanation: Ans: A i.e. Presynaptic block Cl. Botulinum toxin acts by blocking the production/ release of acetylcholine at the synapses & neuromuscular junctions