Answer: C) Large objects clumped together due to gravity to form larger objects.
Any mass, no matter how big or small, exerts a force of gravity on other masses. The larger the mass, the more gravitational force is applied. If you had various objects floating in space, then eventually those objects will collide with one another (if they are close enough). Those collisions effectively clump the materials together to form larger masses. Apply this idea multiple times over a very long timespan, and eventually you go from millions of pebbles to larger rock formations to massive asteroids and so on. If you have enough material, then a planet may be formed under the right conditions. This idea applies not just to solid material, but to gasses as well. Planets such as Jupiter is an example of this.