Doppler Measurements of the Motions of Stars in Nearby Spiral

Doppler measurements of the motions of stars in nearby spiral and barred galaxies indicate that

A) in most spiral and barred galaxies, the arms trail behind the rotating nucleus.
B) in most spiral and barred galaxies, the arms rotate ahead of the nucleus; that is, spiral and barred galaxies are mostly leading-arm galaxies.
C) in most spiral and barred galaxies, the arms lead the rotation of the nucleus; that is, the arms spin faster than the nucleus.
D) about half of all galaxies have trailing arms-the stars rotate slower than the nucleus-while in the other half, the arms rotate ahead of the nucleus.