You are presented with the question "What accelerates an object?" and the following answer choices: 
- transportation technology
 - chemical messengers
 - kinetic energy
 - electromagnetic energy
 - gravitational force
 - flow of electrons
 - a hydraulic system
 - heat energy

Now knowing that the mass of an object causes the gravitational force exerted by that object and gravity accelerates mass, choose the best answer.


 

     gravitational force    