This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology (RNA Virus Pa-1,2 & Miscellaneous Viruses), Subject name: Microbiology
A 5-year-old girl is brought to your Primary Health care Centre of St. Johns office by her mother who states that the child has a runny nose, barking cough, and a sore throat. Your examination indicates that respiration is laboured. None of her three siblings is sick. The most probable viral cause of her symptoms is: 
Select and explain. 
A. Adenovirus, B. Influenza virus, C. Parainfluenza virus, D. RSV
C: Parainfluenza virus
Answer: C: Parainfluenza virus 
Explanation: The child's symptoms are those found with croup caused by Parainfluenza virus. Acute Laryngo-Tracheo-Bronchitis / Croup: Causative organism:Parainfluenza virus type I and II. Symptoms: Upper respiratory tract infection with Hoarseness and croupy cough. Fever 39-40oC. Difficulty in breathing and inspiratory type of stridor. Signs of upper airway obstruction. Steeple Sign on X-ray.