Which of the Following Hypothetical Viruses Would Likely Show a "Cactus-Shaped

Which of the following hypothetical viruses would likely show a "cactus-shaped" population phylogeny?

A) A mutualistic virus that is vertically transmitted
B) A highly virulent virus, like Ebola, that kills its host before the build-up of any immunity
C) A highly virulent virus that results in life-long immunity and that can only infect naïve individuals (e.g., young children) that have never encountered any of the virus's strains
D) A virus that can reinfect previously infected hosts via escape mutants