Here's a problem to solve: Uranus is one of the outer planets of the solar system. The average distance of Uranus from the Sun is 2.87 billion kilometers. Which best explains why Uranus revolves in its orbit instead of moving out into space?

Among the 4 following options, which is the correct answer?

- A: The orbit of Neptune limits Uranus.
 
- B: Gravity pulls Uranus toward the Sun.
 
- C: Electromagnetic energy pulls on Uranus.
 
- D: Other planets have the same mass as Uranus.
 