The answer is the third one
Explanation:
As we age, our immune systems develop defenses against antigens and fights off lots of infections which could harm us.Our body makes lots of T cells when we are young, but slows down production after puberty. Nevertheless, the numbers of these cells in our body stays the same even when we are old. Our body changes in aging process like composition and structural elements of tissues, gone through puberty, your hormones increase, also your metabolismm developed rapidly, structure of your bones developed, etc.
