During which phase of the cell cycle does DNA duplicate?

The correct choice is B, as DNA duplication occurs specifically during the S Phase of the cell cycle. During the S Phase, or Synthesis phase, each chromosome is replicated to create two sister chromatids for each chromosome. This process is crucial because it ensures that when the cell divides, each daughter cell will receive an exact copy of the genetic material, maintaining the chromosome number and genetic fidelity.

In contrast, the G1 Phase is primarily focused on cell growth and normal metabolic processes, while the G2 Phase involves further preparation for mitosis but does not include DNA replication. The M Phase, which includes mitosis and cytokinesis, is the stage where the cell actually divides but has already completed DNA replication prior to this phase during the S Phase. Hence, S Phase is the only stage specifically designated for the replication of DNA in preparation for cell division.