Nuclear fusion involves which of the following processes?

Nuclear fusion is the process in which two light atomic nuclei combine to form a heavier nucleus, releasing a significant amount of energy in the process. This phenomenon is not limited to just combining particles; it involves overcoming the repulsive forces between positively charged nuclei due to their protons.

In stars, for instance, nuclear fusion is what powers them, as lighter elements like hydrogen fuse together to create helium, releasing energy that we receive as sunlight. This process highlights why the joining together of two nuclei to create a larger nucleus is the fundamental characteristic of nuclear fusion and is the reason it is a source of considerable energy.

The other options describe different nuclear processes such as fission (the breakup of a nucleus), neutron capture, and radioactive decay, which do not pertain to the fusion process. Fusion specifically revolves around the creation of larger nuclei from smaller ones, making the correct answer a clear reflection of the definition and characteristics of nuclear fusion.