Answer:
Accretion
Step-by-step explanation:
The Nebular also known as blank theory suggest that Protoplanets began to form around the protosun from many collisions and combinations of gas and natter called Accretion.
Protoplanets are basically extremely small planets that have the size very similar with the size of moon. It is commonly viewed by astronomers that some celestial objects were formed during the process of formation of solar system that are now considered as protoplanets. They were a whirling cloud of gas and dust that condensed down and formed this combination of matter and gas called Accretion.
Hope it help!