1 answer
(click or scroll down)
The statement is partially correct but not complete. To form a nebula, **gravity** does indeed pull matter together; however, it's more accurate to say that gravity causes a **collapse of gas and dust**, leading to the formation of a nebula. **Pressure changes** can occur in the process, but the primary driving force is gravity.
So, while your statement contains some correct elements, it would be better phrased as: "To form a nebula, gravity pulls matter together."