Answer
E - I, II, and III are all causes of declining global diversity.
Work Step by Step
Pollution, habitat loss, and overharvesting all cause declining global diversity as they all remove genes from species' gene pools. The loss of individuals is also a loss in genetic diversity and therefore biodiversity, as individuals have unique (usually) genomes due to recombination. Pollution, habitat loss, and overharvesting can cause many species to become extinct, especially if they are niche specialists.
Therefore I, II, and III are all correct.
