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: Biochemistry
In cholesterol synthesis, which is rate limiting amino acid: 
Select and explain. 
A. HMG CoA reductase, B. HMG CoA synthetase, C. 7 alpha hydroxylase, D. Phosphofructokinase
A: HMG CoA reductase
Answer: A: HMG CoA reductase 
Explanation: A i.e. HMG COA reductase