What is the transfer of energy from one level of the energy
a. productivity
b. net primary productivity
c. ecological efficiency

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.

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d. planting trees

the trees take in carbon to make oxygen.