<prompt> Regurgitation of food back from stomach into oesophagus is prevented byPinch cock effect of diaphragmNegative intrathoracic pressureOesophagogastric angleAll of the above  <response>: Regurgitation of food back from stomach into oesophagus is prevented by: i tone of gastro-oesophageal sphincter, ii negative intrathoracic pressure, iii pinch-cock effect of diaphragm, iv mucosal folds, v oesophagogastric angle and vi slightly positive intra-abdominal pressure. Ref:- Dhingra; pg num:-341 