Your immune system consists of that fight disease.
a.
cells
c.
organs
b.
tissues
d.
all of the above

ANSWER IS D

D

Explanation:

All of the above

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 : )

c. heat from the poles back down towards the equator.