This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oesophagus, Subject name: Surgery
24 hour pH manometery is gold standard investigation for? 
Select and explain. 
A. Hiatal hernia, B. Barrett's esophagus, C. Reflux esophagitis, D. Esophageal ulcers
C: Reflux esophagitis
Answer: C: Reflux esophagitis 
Explanation: ANSWER: (C) Reflux esophagitisREF: Sabiston 18th ed p. 1112The gold standard for diagnosing and quantifying acid reflux is 24 hour pH test, and 24 hours pH score is DeMeester score