4. What are the four components of the Earth system?

Lithosphere (land), hydrosphere (water), biosphere (living things), and atmosphere (air)

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.

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 : )