The right answer is: c. Anaphase.
Anaphase is a very rapid phase of meiosis and mitosis where sister chromatids (during mitosis or meiosis II) or homologous chromosomes (during meiosis I) separate and migrates to opposite poles of the cell.
These sister chromatids are associated with each other after the duplication by the action of a molecule called cohesin. Dysfunction of this protein may cause a number abnormality in the proteins after mitosis or meiosis. There will be no separation of the 2 sister chromatids.