The DNA replication occurs in

Explanation-

Cell division takes place through two processes-
Mitosis and Meiosis

Mitosis is an equational division. Here the chromosomes are equally distributed among the two daughter cells, whereas meiosis, is a reductional process here the chromosome number is distributed half to the daughter cells.

In the case of both mitosis and meiosis, the first phase is the Interphase.
In the interphase cell gets ready for further phases.

In G1-Phase- (First growth phase)
1. Cell is metabolically active, and RNA and proteins are synthesized.
2. Growth of the nucleus takes place

In S-phase-(Synthetic phase)
1. Chromosomal replication, DNA content doubles, and chromatin fibers are formed.

In the G-2 phase-(Second growth phase)
The formation of RNA and protein continues, and both cell and nucleus grow in size.

Final Answer-

So, The correct option is B.