Answer:
The correct answer would be sexual reproduction.
Sexual reproduction leads to the development of genetic variation in the offspring in two ways:
Crossing over: Exchange of genetic material between non-sister chromatids of homologous chromosomes takes place during the formation of gametes.
Fertilization: The two gametes fertilize to form a zygote. Thus, the genetic material of zygote is contributed by both the parents.
These two factors form a new combination of genes in an offspring which is different from either parent.