The correct answer is T helper cells. <span>T helper cells are important because they have the ability to stimulate other cells to kill the foreign particles (viruses, bacteria, fungi, parasites).T helper cells help other cells in the immune response by recognizing foreign antigens and by secreting cytokines that then activate T and B cells.</span>
All the other answer choices are still dreamt of by many scientists and engineers. but you always see people wearing prosthetic legs. D is the obvious answer.
