What occurs during the S phase of the cell cycle?

During the S phase of the cell cycle, DNA replication takes place, which is crucial for ensuring that when a cell divides, each daughter cell receives an identical set of chromosomes. This phase is part of interphase, which occurs before the actual cell division (mitosis or meiosis) happens.

During the S phase, the cell duplicates its chromosomes, resulting in two identical copies known as sister chromatids. Each chromatid is attached to its identical twin at a region called the centromere. This replication is essential for genetic continuity, allowing for proper distribution of genetic material to the daughter cells during cell division.

The other phases and processes mentioned, such as cell division, cell growth, and cytoplasmic division, occur before or following the S phase, specifically during M phase (mitosis) and G1/G2 phases of interphase. Thus, option B specifically highlights the key event of the S phase, which is the duplication of the cell's genetic material.