The correct option is B Prophase I
Crossing over or Chromosomal crossover
is the exchange of genetic material between homologous chromosomes resulting in recombinant chromosomes.
The chromosomes segregate during Meiosis I which is made up of prophase I, Metaphase I, Anaphase I, and Telophase I. The Prophase I is further differentiated into 5 stages- Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis. During
the Pachytene phase of Prophase I homologous chromosomes pair up and become attached to one
another. At this time, crossing over takes place which involves the movement of sections of DNA between the non-sister chromatids of
homologous chromosomes and allows for independent assortment.