The correct answer is D. Gravity pulled particles of dust and gas together to form planets.
Step-by-step explanation:
Gravity is a force of attraction that acts in all universe, and makes objects with more matter attract objects with less matter. This force played an important role in the formation of our solar system. Because it is believed after the big bang occurred, there was a massive cloud of dust, gas, and particles (nebula) and due to the force exerted by gravity, these particles were pulled together forming clumps of different sizes and characteristics that were later the planets, moons and other structures that remain until today. Also due to the force of gravity the sun was formed and planets orbit around it. According to this, the role of gravity in the formation of our solar system was gravity pulled particles of dust and gas together to form planets.