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': 'Vitamin B12 acts as a coenzyme to which one of the following enzymes? \nSelect and explain. \nA. Isocitrate dehydrogenase, B. Homocysteine methyl transferase, C. Glycogen synthase, D. G-6-P dehydrogenase', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]