During S phase of the eukaryotic cell cycle, what major event occurs in preparation for cell division?

• A. The cell undergoes cytokinesis, physically splitting into two daughter cells.
• B. The cell performs most of its growth and normal metabolic functions without DNA replication.
• C. The nuclear envelope breaks down and chromosomes align at the metaphase plate.
• D. The cell replicates its DNA, producing sister chromatids for each chromosome.

Answer: (D)