This question is very good
<span>Cytotoxic t-cell subpopulations are specialized to combat intracellular pathogens, whereas helper t-cell subpopulations are specialized to combat extracellular pathogens.
</span>Cytotoxic t-cell are CD8+ cells. Cytotoxic t-cell uses granzymes to <span>kill </span><span>intracellular bacteria, that lives in the cytosol such as viruses. They identify the pathogen forgein peptids that are bounded to MHC-I on the cell surface.
</span>
cd4+ T helper (Th) cells include Th1, Th2, and Th17 cells. They contribute to aliergic reactions and fighting extracellular parasites.
Human and the natural ones can change the ecosystem
The answer is D: poaching, since it harms wildlife and destroys ecosystems.
