An object's motion changes
a.
when the forces acting on the object remain balanced.
b.
only if the object is at rest when a force acts upon it.
c.
only when a nonzero net force is applied to the object.
d.
all of these

The answer is D, because if the all of them will either stop the object in motion or move an object that is staying still.

Explanation:

answer; i believe the correct answer is ( proteins );

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 : )