Mutations is the global answer to this question nonetheless mutations can happen in many circumstances and each case has a proper name. When the number of chromosomes increases we are talking of polyploidy and this commonly occurs during the meiotic process in the first division during prophase in the crossing of chromatids. Now with this in mind, we can say that the correct answer is option D, as a non-disjunction process implies that there is no propper segregation during meiosis I, so the new cells will possess an abnormal amount of genetic material.