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 with tumor lysis syndrome (TLS) is taking allopurinol (Zyloprim). Which laboratory value should the nurse monitor to determine the effectiveness of the medication? 
Select and explain. 
A. Blood urea nitrogen (BUN), B. Serum phosphate, C. Serum potassium, D. Uric acid level
D: Uric acid level
Answer: D: Uric acid level 
Explanation: Allopurinol is used to decrease uric acid levels. BUN, potassium, and phosphate levels are also increased in TLS but are not affected by allopurinol therapy.