Asolution is a
a. combination of isotopes.
b. chemical reaction.
c. mixture in which the substances are evenly spread out.
d. mixture in which undissolved substances do not settle out.

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 : )