The number of organelles doubles. Chromosomes must be copied. Four nuclei must be formed. The membrane thickens.
At the end of the mitotic cell cycle, a cell divides into two cells. What must happen before the cell divides?

Options:
- The number of organelles doubles.
- Chromosomes must be copied.
- Four nuclei must be formed.
- The membrane thickens.

Chromosomes must be copied.