This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
Most common cause of common cold is? 
Select and explain. 
A. Virus, B. Bacteria, C. Fungus, D. Allergic
A: Virus
Answer: A: Virus 
Explanation: Ans. (a) VirusRef: Harrison 18/e, chapter 186