You are answering a USMLE-style medical question. Question: An investigator is studying the function of different enzymes in various human cell types. A subset of normal human cells with an elevated intracellular concentration of bisphosphoglycerate mutase is harvested and isolated. Which of the following is most likely to be absent in these cells? Options: A) α-ketoglutarate dehydrogenase B) Pyruvate kinase C) Glutathione reductase D) Carbonic anhydrase Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.