Which of the following statements best describes what happens during the s phase of the cell cycle?

The cell's DNA is replicated.

Explanation:

In mitosis, a mother cell produces two daughter cells with the same number of chromosomes. This process of cell division allows the reproduction of unicellular organisms and the growth and regeneration of multicellular organisms.

Interphase is a phase of intense biochemical activity that allows chromosomal duplication and cell growth. When the cell is not in cell division, it is said to be in interphase, that is, it represents the whole-cell: with the membrane, organelles dispersed in the cytoplasm and the material gene involved by the nuclear membrane.  It is didactically divided into three periods: G1, S, and G2. S- (from synthesis): DNA synthesis occurs and consequently chromosomal duplication.

a physical change is being made.