Ss would represent the hybrid. Pure genes are PP hybrid would would be Pp
The sentences that make sense are "Volatile liquids are flammable" and "Liquids burn easily."
Designing efficacious norovirus vaccines remains a major challenge due to several factors:
(1) the extreme genetic variability within the norovirus family and within genogroups
(2) the rapid evolution of antigenically dissimilar pandemic GII.4 norovirus strains
(3) the lack of lasting immunity upon natural exposure to noroviruses in at least a proportion of the population.
