Answer:
E) founder effect and genetic drift
Explanation:
Dunkers moved to Pennsylvania and inhabited a new area to develop a new population. This new population might not have the same gene pool and the same allele frequencies for all the genes as present in the original population. The change in the allele frequencies of a population due to the colonization of a new area by a few members is called the founder effect.
The small size of the new population of Dunkers present in Pennsylvania was more likely to be affected by any chance event which could have added more uniqueness to their gene pool. This is called genetic drift. Therefore, the genetic uniqueness of their population from all the other populations and from their original population might be the result of founder effect and genetic drift.