Answer:
Nuclear fusion
Step-by-step explanation:
The reaction shown in the diagram depicts a nuclear fusion.
The reaction expression is given as:
²₁H + ³₁H → ⁴₂He + ¹₀n + energy
This reaction is a nuclear fusion expression. Here two small lighter nuclide to form a product with an attendant emission of a neutron and energy.
The combination of lighter nuclides to form a heavier one is nuclear fusion.
Fusion is different from nuclear fission in which a heavier nuclide splits up.