People with blood type O are considered to be universal donors. That is, they can
donate blood to all other blood types. Using your knowledge of blood types and the immune
system, explain why this is true.

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 : )

i dont know it at allnow im just getting points at this pint