Answer: Picture at the bottom left corner represents nuclear fusion.
Explanation:
Nuclear fusion is a process in which two or more small nuclei combine together to result in the formation of a larger or heavy nuclei along with emission of energy and neutron.
For example, [tex]^{2}_{1}H + ^{3}_{1}H \rightarrow ^{4}_{2}He + ^{1}_{0}n + Energy[/tex]
Thus, we can conclude that picture at the bottom left corner represents nuclear fusion.
