The right option is; prophase
The nuclear envelope disintegrates during prophase.
Prophase is the first stage of mitosis. Mitosis is a type of cell division in which one cell (the parent) divides to create two new daughter cells that are genetically identical to the parent. The stages of mitosis include; prophase, metaphase, anaphase and telophase. During prophase, the cell begins to break down some structures and produce other ones, getting ready for chromosomes division. The chromosomes condense and there is formation of the mitotic spindle. Also, the nuclear envelope breaks down and releases the chromosomes.
