This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autonomic nervous system, Subject name: Pharmacology
What is Ecothiophate? 
Select and explain. 
A. Directly acting cholinergic drug, B. Acetyl cholinesterase inhibitor, C. Anti cholinergic drug, D. Sympathomimetic
B: Acetyl cholinesterase inhibitor
Answer: B: Acetyl cholinesterase inhibitor 
Explanation: Echothiophate is an OP compound which is an irreversible cholinesterase inhibitor Ref: KDT 6th ed pg 105