The first group to exhibit an amniotic egg was the

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

i hope this : )