Which Was a Contribution to Astronomy Made by Copernicus

Which was a contribution to astronomy made by Copernicus?

A) The planets move around the Sun in elliptical orbits.
B) His theory of gravity accounted for the variable speeds of the planets.
C) He laid out the order and relative motion of the known solar system.
D) He discovered the Sun was not at the center of the Milky Way.
E) His telescope revealed the four moons of Jupiter, a model solar system.