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: Microbiology
The respiratory' syncytial virus 
Select and explain. 
A. The respiratory' syncytial virus, B. The para influenza virus, C. The adenovirus, D. The coronavirus
B: The para influenza virus
Answer: B: The para influenza virus 
Explanation: Croup tLarvngotracheobronchitis
o Croup is a viral infection of upper respiratory tract,
o Children between the age of 1-5 years are affected,
o Para-influenza type I virus is the most common causative organism.
o Other viruses implicated in causaction are RSV, influenza virus, Adneovirus and Rhinovirus.