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
Esophageal motility disorder is best diagnosed is? 
Select and explain. 
A. Barium studies, B. Esophagoscopy, C. 24 hour pH monitoring, D. Manometry
D: Manometry
Answer: D: Manometry 
Explanation: <p>Davidson&;s principles and practice of medicine 22nd edition. *Manometry confirms the high pressure non relaxing oesophageal sphincter with poor contractility of the oesophageal body.</p>