Bladder, I believe. But they are saying that my answer must be 20 Characters long...
Explanation:
Option first is the correct one
Answer:
Sperm-egg interaction
Explanation:
The formation of fertilization envelope is well-studied on the model system- sea urchin. It has been shown that, the fertilization envelope is formed after the initial sperm-egg interaction from the egg surface vitelline envelope and the paracrystalline protein fraction which is derived from cortical granules. Secretion from cortical granules, prevents polyspermy.
Biochemical- apart of the second defense system