Answer:
The correct option is 3. Atoms and molecules are added to dust grain, masses of matter form around dust grain, and masses of matter collide.
Explanation:
Two theories explain how planets get formed. One of them is The gravitational instability, and the other one is the Planetesimal Hypothesis.
The planetesimal hypothesis says that a planet formation is a process in which dust particles and gas collide and get stick together in a process known as coagulation. This makes place to grains production. These grains enhance their sizes up to a point in which they form bodies big enough to be called planetesimals. When planetesimals are formed, they start a gravitative interaction with other planetesimals of different sizes, and by collision, they form bigger planetesimals that accrete the smaller ones and end up forming a proto-planet. Planets and giant planets get formed by accretion of solid planetesimals. The term accretion refers to the solids agglomeration to form bigger objects, such as planets.
