This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
Not a Radiological feature of achalasia cardia 
Select and explain. 
A. Megaesophagus, B. Bird beak appearance, C. Rat tailed appearance, D. Antral nipple sign
D: Antral nipple sign
Answer: D: Antral nipple sign 
Explanation: Antral nipple sign - Feature of Congenital hypertrophic pyloric Stenosis.