At what point in the cell cycle does dna replication occur and why? a. during cell division, to ensure that the dna will fit into the resulting cells b. before a cell divides, to ensure that the dna will fit into the resulting cells c. after a cell divides, to provide each of the two resulting cells with a complete set of dna instructions d. before a cell divides, to provide each of the two resulting cells with a complete set of dna instructions