Answer:
The correct answer is - option B. sister chromatids.
Step-by-step explanation:
When a one strand DNA of a chromosome replicates itself into two identical copies of DNA formed, these two identical DNA copies are called as sister chromatids.
Dyad is a pair of sister chromosomes and each sister chromosome have two chromatids. The formation of the sister chromatids takes place in the S phase of interphase which is also called the synthesis phase.
Thus, the correct answer is - option B. sister chromatids.