Question

which event takes place first in the stages before the birth of a star?
gravity pulls gas and dust together.
a protostar forms as mass increases.
nuclear fusion begins under high pressure.
a protostar collapses and becomes denser.

Explanation:

The formation of a star starts when gravitational forces cause gas and dust in space to clump together. This is the initial step before a protostar forms, nuclear - fusion begins, or a protostar collapses further.

Answer:

Gravity pulls gas and dust together.