Answer:
Stellar evolution
Step-by-step explanation:
Nuclear fusion is the process that goes inside a star which powers the star.
Nebular clouds are just clouds of dust (mostly hydrogen and helium) from which a star is born.
Stellar evolution describes the various stages in the life of a star.
The big bang describes how the universe as we know it actually is created. It says universe is created by the explosion of the tiny and highly dense singularity .