This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T., Subject name: Medicine
Bernstein test involves infusion of 0.1 NHCl into the esophagus. This test is used to diagnosis which of the following condition? 
Select and explain. 
A. Achalasia cardia, B. Diffuse esophageal spasm, C. Gastro esophageal reflux disorder, D. Esophageal malignancy
C: Gastro esophageal reflux disorder
Answer: C: Gastro esophageal reflux disorder 
Explanation: Ans. C. Gastro esophageal reflux disorderIn a patient of GERD, infusion of acid produces heartburn, which in a normal individual does not produce any symptom.Ambulatory pH monitoring is the tool to see reflux. Esophagoscopy and biopsy are other diagnostic tools.Best investigation for the diagnosis of GERD is 24 hour Ph monitoring.