In the Rings of Saturn,there Are Two Main Rings,the Outer

Multiple Choice

In the rings of Saturn,there are two main rings,the outer A ring and the inner B ring.How are the particles in these rings seen to move when examined (by Doppler effect of reflected sunlight) from Earth?

A) Particles in the A ring move more slowly than those in the B ring.
B) Speeds of the particles in all rings are the same because mutual gravitational forces between them ensure that they move as a solid disk.
C) Speeds of the particles vary because of attraction by the Sun, so A particles sometimes move faster and at other times B particles move faster.
D) Particles in the A ring move faster than particles in the B ring because they are farther from the planet.