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
An flu is ? 
Select and explain. 
A. Type A, B. Type B, C. Type C, D. Type D
A: Type A
Answer: A: Type A 
Explanation: Ans. is 'a' i.e., Type A An flu (an influenza) is caused by Type A influenza virus with various HN strains.