What is nuclear fusion? What is nuclear fusion? the process of splitting nuclei to produce energy an explosion caused by putting together two volatile chemicals the process of turning matter into pure energy a process that only occurs in bombs the process of combining lightweight nuclei to make heavier nuclei

the process of combining lightweight nuclei to make heavier nuclei

Explanation:

Fusion means to combine two things together. Hence, nuclear fusion is a process involving the combination of two or more nuclei to form a single nucleus that is heavier than each individual nucleus.

Nuclear fission is the opposite of fusion. A heavy nucleus is splitted to produce energy.

The first option is the correct option.