During which phase does DNA replication occur in the cell cycle?

DNA replication occurs during the S phase of the cell cycle. This is a crucial phase where the cell synthesizes an exact copy of its DNA, ensuring that when the cell divides, each daughter cell receives an identical set of chromosomes. The S phase is sandwiched between the G1 phase, where the cell grows and prepares for DNA synthesis, and the G2 phase, where the cell continues to grow and prepares for mitosis. The accurate duplication of DNA during the S phase is vital for maintaining genetic stability and preventing mutations, which could lead to cancer if errors are propagated. Therefore, the S phase is specifically dedicated to this critical process, making it the correct answer.