Answer: The correct answer is-
B. an increase in genetic variation.
Genetic variation occurs in case of sexually reproducing organisms as gene variants ( alleles) in reproductive cells ( gametes) are segregated and randomly fused upon fertilization.
Genes also undergo genetic recombination (during crossing over in homologous chromosomes ) during meiosis ( particularly in Pachytene stage of Prophase 1).
As a consequence, when sex cells randomly combine during fertilization to produce offspring, there is an increase in genetic variation.
Thus, option B) is the right answer.