What are the primary parts of the systemic circuit, and in what order does blood run through them?
the left atrium and ventricle of the heart ® blood vessels
the left ventricle and the aorta ® arteries
the left atrium and ventricle of the heart ® the aorta
the left ventricle and the aorta ® blood vessels

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 breeding ground 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 of why this virus contained 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) related viruses can undergo genetic recombination if the rna genomes mix and match during viral assembly.d) the human was likely infected with various bacterial strains that contained all three rna viruses.