Answer- B. Tracheo-bronchoscopyIsolated tracheoesophageal fistula (TEF) (H-type fistula):Congenital isolated TEF (H-type) is a rare disorder posing diagnostic and management problems.H-type TEF is more frequent than H-type, owing to the oblique angle of the fistula from the trachea (carina or main bronchi) to the oesophagus, anatomically at the level of the neck root (c7-T1).Pressure changes between both structures can cause entry of air into the oesophagus, or entry of oesophageal content into the trachea.