A lizard lays an egg for a new baby lizard.

Asexual reproduction

Sexual reproduction

the answer to your question is:

c. complementary base-pairing

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).