You are answering a USMLE-style medical question. Question: A 65-year-old female patient comes to the physician’s office for her annual check-up. The patient’s only complaint is that she feels her vision has been getting more blurry over the past year. The patient has a past medical history of diabetes diagnosed 20 years ago and osteoarthritis. Her medications include metformin, glimepiride, and ibuprofen as needed for pain. Fundoscopic examination of this patient reveals narrowing of retinal arteries and microaneurysms. This patient’s symptoms are likely caused by tissue specific differences in expression of which of the following enzymes? Options: A) Sorbitol dehydrogenase B) Galactocerebrosidase C) Arylsulfatase A D) Sphingomyelinase Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.