Stars<span> are powered by </span>nuclear fusion<span> in their cores, mostly converting hydrogen into helium. The production of new elements via </span>nuclear<span> reactions is called nucleosynthesis. A </span>star's<span> mass determines what other type of nucleosynthesis </span>occurs<span> in its core (or during explosive changes in its life cycle). READ THIS AND YOU WILL UNDERSTAND I THINK IS TRUE </span>
Nuclear fusion is a thermonuclear reaction in which light stable nuclei combine with each other in order to form a heavy stable nucleus with the release of large amount of energy.
In case of stars, four hydrogen nuclei combine with each other to form a helium nucleus with a release of 26 Mev per cycle.
Thus, nuclear fusion occurs in stars is true statement.