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.

Your awser would be a acetone