Choose the correct statement about precession of Earth's axis:
A. Precession makes Earth's axis of rotation swing around, slowly tracing out a circle in the sky over thousands of years.
B. Precession of Earth's rotational axis does not affect the position of Earth's pole star.
C. The precession of Earth's spin axis is caused by the tidal ebb and flow of ocean waters on Earth.
D. Precession is the motion of Earth along its orbital path.