You are presented with the question "What causes a planet to accelerate?" and the following answer choices: 
- other planets
 - magnets
 - wind
 - gravitational pull
 - flow of electrons
 - It gets heated up
 - heat energy
 - energy of moving objects

Now knowing that the mass of a planet causes the pull of gravity on that planet and gravity accelerates mass, choose the best answer.


 

    gravitational pull     