The correct answers are:
A. He used careful observations of planetary movements and previous astronomical models to formulate his ideas. C. He determined that the Sun, and every other planet revolves around the Earth. (This is actually a misunderstanding; Copernicus proposed that the Earth and other planets revolve around the Sun.)
However, based on the provided options, none of the answers correctly reflect Copernicus's heliocentric model; he did not use a microscope or telescope, as these were not invented or used in his time. His model asserted that the Earth revolves around the Sun, not the other way around.