Rough-skinned newts produce a strong toxin called TTX as a defense mechanism against predators. Garter snakes can tolerate a very limited amount of the toxin. However, several populations of garter snakes have recently shown
an increased tolerance for TTX. The different populations of snakes have independently acquired a gene variation
that allows them to better block the effects of the toxin.

Which of these most likely to increase in garter snakes?

A. The average number of genes in the garter snake populations

B. The number of times a garter snake replicates the variant gene

C. The frequency of the variant gene in the garter snake populations

D. The average number of times genes mutate to create a tolerance for the toxin