The planets in our solar system revolve around the Sun. One revolution is considered to the one year. Year length varies for each planet. The planets DO have one thing in common though. What do they have in common?

Responses
A Day length is the same for all.Day length is the same for all.
B Their orbits are elliptical in shape.Their orbits are elliptical in shape.
C All the planets are solid, orbiting bodies.All the planets are solid, orbiting bodies.
D The force of gravity is constant throughout the solar system.

B Their orbits are elliptical in shape.