After a Thousand Years,Ptolemy's System of Planetary Motion Gave Readings

After a thousand years,Ptolemy's system of planetary motion gave readings that were less accurate than the readings it gave when it was first devised.One main reason for this was that:

A) measuring instruments had improved to the point where small prediction errors could be detected.
B) proper motions of the stars over a millennium had changed their positions.
C) precession had altered the seasonal positions of the planets and constellations.
D) the orbits of the planets have drifted slowly over time.