Fish eggs that are fertilized externally are typically clustered and covered in

Fish eggs that are fertilized externally are typically clustered and covered in a thick, jelly-like substance. What is most likely the function of this substance? to protect the eggs and keep them consistently warm inside the parent's body to protect the eggs and keep them safe from any harmful environmental conditions to ensure that only a few of the eggs are fertilized by sperm since external fertilization is uncommon and risky to ensure that only some of the eggs are fertilized by sperm so others can be fertilized internally