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: Surgery
Best test to diagnose gastroesophageal reflux disease and quantify acid output is: 
Select and explain. 
A. Esohagogram, B. Endoscopy, C. Manometry, D. 24 hr pH monitoring
D: 24 hr pH monitoring
Answer: D: 24 hr pH monitoring 
Explanation: 24 hr pH monitoring "The gold standard, for diagnosing and quantifying acid reflux is the 24-hr pH test." -Sabiston Also Know Using 24-hour pH test an overall score is obtained. It is known as DeMeester score.