How does random fertilization add to the genetic variation?
a)nonsister chromatids exchange gene segments to produce new combinations of maternal and paternal genes.
b)fusion of sperm and ovum, each having a unique combination of chromosomes, introduces further variation.
c)homologous pairs of chromosomes sort into daughter cells independently of the other pairs.

Random fertilization adds to the genetic variation thanks to B)Fusion of sperm and ovum, each having a unique combination of chromosomes, introduces further variation. Fertilization is a process of fusion of sperm and ovum. In a random fertilization, it is expected that sperm and ovum each have a unique combination of chromosomes. Thus, the created zygote will have a unique combination of chromosomes which introduces variation.