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
[{'content': 'Most common cause of common cold is? \nSelect and explain. \nA. Virus, B. Bacteria, C. Fungus, D. Allergic', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) VirusRef: Harrison 18/e, chapter 186', 'role': 'assistant'}]