Answer:
The correct answer is option D, that is, magic numbers.
Step-by-step explanation:
The magic number in nuclear physics refers to the number of nucleons, that is, either neutrons or protons, distinctly, such that their alignment results in the formation of complete shells within the nucleus of the atom. As a consequence, atomic nuclei comprising a magic number of neutrons or protons are much more stable in comparison to other nuclei.
The seven most broadly known magic numbers are 2,8,20,28,50,85 and 126.