Question

which is the final event that occurs when a star is forming?
the outer layer of the star expands.
gravity pulls gas and dust together.
a black hole forms as the core collapses.
nuclear fusion begins under high pressure.

Explanation:

When a star is forming, gravity first pulls gas and dust together. As the core becomes denser and hotter, nuclear fusion (the process of combining light atomic nuclei into heavier ones, releasing energy) begins under high pressure. This is the final event in the star - forming process among the given options. The outer layer expanding is more related to later stages like in red - giants. A black hole forming is a late - stage event for massive stars after their main - sequence and other post - main - sequence phases. Gravity pulling gas and dust together is an early step in star formation.

Answer:

Nuclear fusion begins under high pressure.