‘Noble gases’ are least reactive as their outer shells are fully filled with electrons. These do need to share their electrons from outer shells with other elements .
T<span>he least likely to be a source of genetic variation among living organisms is D. asexual reproduction. Asexual reproduction is a kind of reproduction that does not include fertilization process of two gametes: female and male but only includes parts of plants or cells. In this case, variation is minimized</span>
I think its if one parent has no alleles for the disease.
The answer is D, I hope this helps!! :)