Nondisjunction Is the Failure of Homologous Chromosomes to Separate During

Nondisjunction is the failure of homologous chromosomes to separate during meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis. As a result, both homologous chromosomes or both sister chromatids migrate to the same pole of the cell. This produces daughter cells with an imbalance of chromosomes. A cell biologist examines the final products of meiosis in an earthworm (2n=36) and finds 2 cells with 20 chromosomes, and 2 cells with 16 chromosomes. Most likely this was because

A) 2 pairs of sister chromatids failed to separate during meiosis II.
B) 1 pair of sister chromatids failed to separate during meiosis II.
C) 2 pairs of homologous chromosomes failed to separate during meiosis I.
D) 1 pair of homologous chromosomes failed to separate during meiosis I.