This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdominal Radiography, Subject name: Radiology
Bird beak appearance on barium swallow study in seen in - 
Select and explain. 
A. Achlasia cardia, B. Carcinoma esophagus, C. Hiatus hernia, D. Diffuse esophageal spasm
A: Achlasia cardia
Answer: A: Achlasia cardia 
Explanation: Ans. is 'a' i.e., Achlasia cardia o ''Bird beak appearance on barium study is seen in achlasia cardia.Important esophageal signsSignConditionRat tail appearance of esophagus MaharashtraEsophageal carcinomaMegaesophagus (sigmoid esophagus)"Bird beak" appearanceHurst phenomenonAchalasia cardiaYo-Yo motion of barium "Corkscrew" appearance(esophageal curling)Rosary-bead/sheikh kebab configurationChain of bead appearanceDiffuse esophageal spasm