If the Original Finches That Had Been Blown Over to the Galapagos

If the original finches that had been blown over to the Galapagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galapagos, this would have been an example of

A) genetic drift.
B) bottleneck effect.
C) founder's effect.
D) all three of these
E) both A and C