Answer:
Option D is correct.
Step-by-step explanation:
Saturn's rings are formed by thousands of ice blocks which vary in size from microscopic to as big as a car.
The particles spinning around the planet have a constant orbital velocity that continuously pushes them out to space, but Saturn's strong gravitational force pulls them towards the planet keeping the rings in line as it has done for approximately 100 million years, and will continue to do so for another 300 million years.
If by chance a particle changes its orbital angle, the gravity pull will be too strong for the particle to escape and will slowly correct its orbit over time.