The X-shaped structure you are referring to represents the replicated chromosomes, which consist of two sister chromatids connected at the centromere. This structure is typically observed during specific stages of mitosis.
In mitosis, you would see the X-shaped chromatids during:
- End of prophase: where the chromosomes condense and become visible as distinct structures.
- Metaphase: where the chromosomes align at the metaphase plate.
Therefore, the correct answer would be:
d. end of prophase and metaphase.
During these phases, the chromosomes are clearly organized in the X-shape. Other phases, such as interphase, do not show this structure, and during anaphase, the sister chromatids are being pulled apart, so they would not be in the X-shaped form either.