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: Medicine
A 55- year old diabetic patient presents with transient obscuration in vision for 2-3 days followed by sudden loss of vision. Which of the following would be the best test to evaluate the symptoms? 
Select and explain. 
A. Serum ACE levels, B. Quantiferon-Gold TB test, C. Elevated homocysteine levels, D. Serum creatinine levels
D: Serum creatinine levels
Answer: D: Serum creatinine levels 
Explanation: Answer- D. Serum creatinine levelsDM can lead to both retinopathy and nephropathy, Serum creatinine levels would be the best for kidney function and evaluation of patient symptoms.