This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pharmacology
'Lock and Key model' of enzyme action was proposed by 
Select and explain. 
A. Emil Fisher, B. Daniel Koshland, C. Lenor Michaelis, D. Maud Menten
A: Emil Fisher
Answer: A: Emil Fisher 
Explanation: Lock and key hypothesis By emil Fischer Active site is rigid Substrate has complimentary shape Demerits: 1. Rigid active site in reversible reaction. 2. Stabilization of transition state Ref: G n G 13th ed.