Between 1919 and 1956, human Influenza was caused by viruses of H2N2 subtype, and there was a new pandemic. Which of the following processes was most likely responsible for the appearance of H2N2 virus?
- a. Point mutations from error-prone viral RNA polymerase to generate a new subtype
- b. Acquisition of the RNA segment that encodes a new subtype of NRA polymerase
- c. Reactivation of latent H2N2 viruses in human carriers
- d. Gene reassortment between human and animal influenza viruses