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
Elevated serum amylase usually returns to normal after 7 days of acute pancreatitis. If it remains elevated after 7 days, the possible causes include all except: 
Select and explain. 
A. Pancreatic ductal disruption, B. Pancreatic ductal obstruction, C. Pseudocyst formation, D. Chronic calcific pancreatitis
D: Chronic calcific pancreatitis
Answer: D: Chronic calcific pancreatitis 
Explanation: In acute pancreatitis, the serum amylase and lipase are elevated within 24 hours of onset and remains for 3-7 days. Levels return to normal within 7 days unless there is pancreatic ductal disruption, ductal obstruction, or pseudocyst formation. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 2631