the size of the planets gravitational pull of the Sun the composition of the planets electromagnetic radiation from the Sun
I gave my students this multiple choice question: Planets in the solar system are in constant motion. What factor has the greatest effect on the orbits of the planets?

Only one answer is correct among these 4 choices:
- the size of the planets
- gravitational pull of the Sun
- the composition of the planets
- electromagnetic radiation from the Sun

Could you tell me which one is correct?

gravitational pull of the Sun