3.
a
b
c
d
heat from which of these causes
convection currents inside earth?
crust
crust and mantle
crust and core
mantle and core

I believe mantle and core, heat rising and falling inside the mantle creates convection currents generated by radioactive decay in the core.

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 : )