Answer: The correct answer is gravity.
Step-by-step explanation:
Gravity is a force by which one object attracts the other object towards its center.
Gravity keeps all of planet in the orbit around the sun. Higher the mass of the object or body , more will be the force of gravity.
Sun has more mass as compared to the other planets. The Sun pulls the all other planets towards its center. Therefore, all planets revolves around the Sun.
Therefore, the planets are pulled towards the Sun by gravity.