Which of the following is the most common mechanism of genetic variation in the population of a sexually-reproducing organism?

Homologous recombination is a significant source of variability. During meiosis in sexual organisms, two homologous chromosomes cross over and exchange genetic material. It is a process by which pieces of DNA are broken and recombined to produce new combinations of alleles. This recombination process creates genetic diversity at the level of genes that reflects differences in the DNA sequences of different organisms. So, the correct answer is option B.