The foundation for biological evolution or descent through modification is

 A)  changes in gene frequency in a population occur from one generation to the next.

The foundation of biological evolution is changes in gene frequency in a population occur from one generation to the next. Mutation, migration, genetic drift, and natural selection along with sexual reproduction result in genetic variation or changes in gene frequency.

~Gotten from USATestprep~

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 : )