Question

which of these is a by - product of nuclear fusion? air helium radiation

Explanation:

Nuclear fusion is a process where light atomic nuclei combine to form a heavier nucleus. In the case of hydrogen - hydrogen fusion (common in stars like the Sun), helium is produced as a by - product. Air is a mixture of gases (mainly nitrogen and oxygen) and is not related to nuclear fusion. Radiation is more associated with nuclear fission (where a heavy nucleus splits) or radioactive decay, not as a by - product of nuclear fusion in the sense of a new element formation.

Answer:

helium