In a controlled experiment, how many variables are changed/ manipulated
from the control group to form the experimental group?

A) no variables are changed
b) only one
c) two or more
d) all variables

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 : )

i dont know it at allnow im just getting points at this pint

since there are no options posted i'll give you a few examples.

a dolphin's flipper, bird's wing, cat's leg.