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
Investigation to diagnose the Laryngo pharyngeal reflux 
Select and explain. 
A. Esophageal pH monitoring, B. Dual Probe Impedance pH monitoring, C. Barium Esophagogram, D. Scintigraphy
B: Dual Probe Impedance pH monitoring
Answer: B: Dual Probe Impedance pH monitoring 
Explanation: Ans. (b) Dual Probe Impedance pH MonitoringRef: Shackelford Page 222/8th Edition* pH monitoring at the level of Pharynx is not helpful because the acid refluxed is neutralized by the Pharyngeal secretions.* Hence a Dual (Bifurcated) catheter measuring both pH and Impedance is used across Upper esophageal sphincter, thereby permitting detection of Pharyngeal reflux