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
[{'content': 'Rate limiting step in cholesterol synthesis is: \nSelect and explain. \nA. HMG CoA synthetase, B. HMG CoA reductase, C. Thiokinase, D. Mevalonate kinase', 'role': 'user'}, {'content': 'Answer: B \nExplanation: HMG CoA reductase', 'role': 'assistant'}]