Final answer:
Option D: A chromatid refers to either a dyad or a monad and represents one of the two identical copies of a chromosome, connected at a centromere. Chromatids separate during anaphase II of meiosis.
Step-by-step explanation:
The term that can refer to either a dyad (pair of sister chromatids) or a monad (single chromatid) is d) Chromatid. A chromatid is one of two identical copies of a chromosome that are joined together at a centromere before a cell divides. During the S phase of interphase, the chromosomes replicate, leading to the formation of sister chromatids. They are held together by cohesin proteins and are most closely connected in the centromeric region, which is highly condensed and can be seen as a constricted area under a light microscope.
The separation of sister chromatids occurs during anaphase II of meiosis, where the kinetochore microtubules pull sister chromatids apart, moving them toward opposite poles of the cell.