Choose the correct statement about precession of the Earth's axis.

A. Precession of the Earth's axis of rotation is caused by changes in the shape of the Earth's orbit due only to the gravitational pull of the Sun.
B. One complete cycle of the Earth's pole star is not affected by precession.
C. One cycle of the precessional motion of the North Celestial Pole takes about 26,000 years.
D. Precession is the motion of Earth along its orbital path.