Answer:
The most appropriate answer would be D) crossing over of homologous chromosomes during meiosis.
Crossing over is the event that takes place during the pachytene stage of prophase 1 of meiosis 1.
During this event, genetic material is exchanged between the non-sister chromatids of the homologous chromosomes.
The homologous chromosomes assemble near each other in a synapsis. The tetrad or bivalent is formed during this period.
The point of contact where the actual exchange of genetic material takes place is termed as chiasma.
Crossing over results in new combination of genes different from either parent.