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
Which of the following enzymes require NAD as cofactor? 
Select and explain. 
A. Citrate Synthase, B. Isocitrate Dehydrogenase, C. a-Ketoglutarate dehydrogenase, D. Succinate Thiokinase
C: a-Ketoglutarate dehydrogenase
Answer: C: a-Ketoglutarate dehydrogenase 
Explanation: a-Ketoglutarate dehydrogenase REF: Harper 27th ed p. 496 NAD is cofactor in: Lactate dehydrogenase Pyruvate dehydrogenase Alpha ketoglutrate dehydrogenase