Humans possess two alleles, or variations, for each gene. the alleles may be the same, or they may be different. when humans reproduce, their alleles are separated and independently sorted into different gametes, or sex cells. so, when sex cells randomly combine during fertilization to produce offspring, there
a. a low probability of survival.
b. an increase in genetic variation.
c. a decreased risk of mutation.
d. a high probability of producing a clone.

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.