The Reason for the Slow Drift of the Position of the Vernal

Multiple Choice

The reason for the slow drift of the position of the vernal equinox through the sky against the background stars over long periods of time is the

A) motion of Earth in its orbit.
B) overall movement of local stars in the sky.
C) movement of the Sun in the Milky Way Galaxy.
D) precession of the spin axis of Earth.