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
A 2 yrs old boy, is brought with sudden onset of stridor and respiratory difficulty. The chest examination reveals decreased breath sounds and wheeze in the right side. The chest X-Ray showed an opaque right hemithorax. Which of the following is the most likely diagnosis: 
Select and explain. 
A. Pneumothorax, B. Acute epiglottitis, C. Massive pleural effusion, D. Foreign body aspiration
D: Foreign body aspiration
Answer: D: Foreign body aspiration 
Explanation: Foreign body inhalation is most common cause of acute collapse with peak age incedence in 1-2 years. Ref: Textbook of Pediatrics By K.N Agarwal, 2010, Page 235