This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pediatrics
A newborn infant was referred with intermittent cyanosis which improved on crying but worsened when quiet. What is the most likely dignosis ? 
Select and explain. 
A. Diaphragmatic hernia, B. Congenital hea disease (Cyanotic), C. Choanal atresia, D. Tracheal agencies
C: Choanal atresia
Answer: C: Choanal atresia 
Explanation: In choanal atresia cyanosis relieves when baby stas mouth breathing, that is on crying. Ref : Ghai essential of pediatrics, eighth edition, p.no:366