C. Gravity acts on all objects in the universe.
Step-by-step explanation:
Isaac Newton with his studies understood that the force of gravity acts on all objects with mass in the universe, and it is the same force that causes an apple to fall from a tree and that keeps the Earth in motion around the Sun.
Newtons also created a formula that allows us to calculate the force of gravity between two objects:

where
G is the gravitational constant
m1 and m2 are the masses of the two objects
r is the separation between the two objects