In 2009, a Flu Pandemic Was Believed to Have Originated

In 2009, a flu pandemic was believed to have originated when viral transmission occurred from pig to human, thereby earning the designation "swine flu." Although pigs are thought to have been the host for the 2009 virus, sequences from bird, pig, and human viruses were all found within this newly identified virus. What is the most likely explanation for the presence of sequences from bird, pig, and human viruses?

A) The virus was descended from a common ancestor of bird, pig, and human flu viruses.
B) The infected individuals happened to be infected with all three virus types.
C) The RNA of related viruses can reassort during viral assembly resulting in new genetic combinations.
D) The human was likely infected with various bacterial strains that contained all three RNA viruses.