Final answer:
After the S phase, a human cell contains 46 pairs of sister chromatids and 92 individual DNA molecules, as each of the 46 chromosomes duplicates into two chromatids attached at the centromere.
Step-by-step explanation:
The correct option : d
During the S phase, each of the 46 chromosomes is replicated, forming two identical chromatids. These sister chromatids stay attached to each other at their centromere through proteins known as cohesins. As a result, after the S phase and before cell division, there are a total of 92 chromatids present in a cell, accounting for 46 pairs since each chromosome now consists of two chromatids.
The term "pair of sister chromatids" refers to the two identical halves of a single replicated chromosome, while "individual DNA molecules" pertains to each chromatid bearing a DNA molecule. It is essential not to confuse sister chromatids with a homologous pair of chromosomes, which are two different chromosomes inherited from each parent.