How does nuclear fusion occur in stars?

Nuclear fusion in stars is primarily how they produce energy and light, and this process mainly occurs in their cores, where high temperatures and pressures are found. The correct answer indicates that hydrogen nuclei combine to form helium. During this fusion process, four hydrogen nuclei (protons) undergo a series of reactions that ultimately yield one helium nucleus, along with the release of a significant amount of energy in the form of gamma rays.

This energy release is due to the conversion of mass into energy, as described by Einstein’s famous equation (E=mc^2). In essence, the mass of the resultant helium nucleus is slightly less than the total mass of the four protons, with the missing mass converted to energy. This process is what powers stars and counters the force of gravity, enabling them to maintain their structures and emit light.

The other choices reflect processes that either do not typically occur in stars or misrepresent fusion. For instance, while oxygen fusion does occur in more massive stars during later stages of their lifecycle, it is not the dominant fusion reaction in most stars where hydrogen fusion predominates. The mention of helium nuclei splitting into hydrogen and releasing energy is an incorrect representation of nuclear reactions; in fact, fusion involves combining lighter nuclei rather than splitting