What agent of erosion is this? Gravity, wind, waves, running water or glaciers.

The higher the proportion of loci that are "fixed" in a population, the lower is that population'sa) nucleotide variability only.b) genetic polyploidy only.c) average heterozygosity only.d) nucleotide variability, average heterozygosity, and genetic polyploidy.e) nucleotide variability and average heterozygosity only.