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
Virus which has more than one serotypes - 
Select and explain. 
A. Measles, B. Mumps, C. Rubella, D. Influenza
D: Influenza
Answer: D: Influenza 
Explanation: Ans. is 'd' i.e., Influenzao Influenza virus is an enveloped RNA virus containing 8 pieces (8 segments) of single stranded RNA.o There are three viral subtypes : (i) Type A (causes all pandemics and most epidemics); (ii) Type B: and (iii) Type C (not circulating currently).o Currently the influenza viruses circulating in the world are : H1 N1 of type A (causes swine flu); H2N2 of type A; H3 N2 of type A; H5N1 of type A (causes birdflu or avian influenza); H7 N9 of type A (caused epidemic of avian influenza in China in 2013); and type B.