Answer:
The most appropriate reason for the presence of genetic diversity among siblings would be an option A.
Crossing over is an event that place during pachytene stage of prophase I. During this event, the genetic material is exchanged between the non-sister chromatids of homologous chromosomes.
It results in the production of a new combination of alleles in gametes. These combinations can be different from either parent.
So, when genetically varied gametes fused to form a zygote, it results in the development of genetic variation among population including siblings.
