DNA replication occurs during the cell cycle in preparation for mitosis. The double helix is unzipped by the helicase enzyme, and DNA polymerase binds nucleotides to each strand using complementary base pairing. During which phase of the cell cycle does DNA replicate, and which model is used?

A. G1 phase; conservative

B. G2 phase; dispersive

C. Metaphase; semiconservative

D. S phase; semiconservative