Cells responsible for innate immunity are activated most commonly by ... A. glucocorticoids. B. epitopes on antigens. C. cytoplasmic proteins of bacteria. D. antigen presentation via MHC proteins. E. carbohydrate sequences in bacterial cell walls.

The answer is C. cytoplasmic proteins of bacteria

Explanation:

The immune system includes innate immune responses and adaptive immune responses.

Innate immunity: rapidly act against strange toxin or invaded microbes. It evolves membrane bound receptors and cytoplasmic proteins that present on the surfaces of invading microorganisms. Adaptive immunity: it expresses exquisite specificity for target antigens.