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
The 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: "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 the DeMeester score.