Just changed and transferred
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>
If a species is said to be extinct, then that species is reduced to zero. There are none living in existence. The affects to other organisms of its extinction would depend on their value to the ecosystem. Regardless, extinction completely stops evolution of the species extinct.
