The nuclear equation 2 1h 3 1h → 4 2he 1 0n is an example of 1. a chain reaction. 2. a branching chain. 3. nuclear fission. 4. nuclear fusion

I believe the reaction shown in the question is an example of nuclear fusion.
Nuclear fusion is a nuclear reaction in which two or more atomic nuclei collide at a very high energy and fuse into a new nucleus. An example of nuclear fusion; is the nuclear fusion in the sun; where the sun is composed of lots of hydrogen and by the fusion of two isotopes of hydrogen; helium is produced and in turn energy is released.

You know how the first one if filled up like the objects do the same but with the other categories

Fine out you self hx