Statement (A) is correct because in eukaryotic cells, DNA replication takes place inside the nucleus during the S-phase of the cell cycle.

Statement (B) is incorrect as G₂ phase is termed the post-synthetic phase (following DNA synthesis), not post-mitotic; post-mitotic refers to the stage after mitosis.

Statement (C) is incorrect because crossing over occurs during the pachytene stage of meiosis, and chiasmata are the visible manifestations of crossing over seen later in diplotene. Thus, chiasma formation is a result, not the cause.

Statement (D) is correct and is a fundamental principle of cell theory stating that all cells arise from pre-existing cells through cell division.

Hence, only statements A and D are correct.