New allele combinations are acted upon by natural selection.
Explanation:
Recombination may be defined as the process of the exchange of the genetic material between the homologous chromosomes of the non sister chromatid. The combined trait will be visible in the upcoming generation.
The recombination allows the generation of the new genes in the population. These new genes if beneficial for the population will be pass to the next generations. The new allele will be favored by the natural selection and increases the chance of survival of the population.
Thus, the correct answer is new allele combinations are acted upon by natural selection.