Hardy-Weinberg equilibrium is known to be affected by gene flow, genetic drift, mutation, genetic recombination and.

The correct option is C Natural selection

• The Hardy-Weinberg principle states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.
• When mating is random in a large population with no disruptive circumstances, both genotype and allele frequencies will remain constant because they are in equilibrium.
• Any factor, which can disturb the alleles in a population is likely to affect the Hardy-Weinberg equilibrium.
• The alleles in a population can be altered by mutation, migration, genetic drift, recombination, and natural selection. Hardy-Weinberg equilibrium is not effected by evolution, limiting factors, saltation and over prediction

So, the correct answer is 'Natural selection'.