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:

During star formation, gravity first pulls gas/dust together (initial step). As the protostar's core compresses, pressure and temperature rise. The final step of star formation is when these conditions are high enough to ignite hydrogen nuclear fusion, which marks the birth of a stable star. Expanding outer layers happen later in stellar evolution, and black holes form from massive star deaths, not formation.

Answer:

D. Nuclear fusion begins under high pressure.