why does being an obligate intracellular pathogen considered a virulent factor?

A. these pathogens are able to evade the cellular immune response and can be eliminated by the presence of humoral antibodies

B. these pathogens can reside practically both inside and outside of the cell whenever deemed necessary

C. these pathogens can quickly adapt to extracellular environment

D. these pathogens are able to evade the humoral antibodies and can be eliminated by a cellular immune response