Hi!
I would say C, weak, dead, or partial antigens because do you need to be introduced to the disease for your body to fight it.
Hope this helps!
<em>T</em><em>he smallest unit into which a substance can be divided without changing its chemical </em><em>nature</em>
<em>Hopes </em><em>this </em><em>helps</em><em> uh</em><em> ♥️</em><em>♥️</em>
Answer:
Parts of the reproductive system. image attached