The Observation That Island D

The observation that island D.yakuba are more closely related to mainland D.yakuba than island D.yakuba are to D.santomea is best explained by proposing that D.santomea

A) descended from a now-extinct non-African fruit fly.
B) arrived on the island before D.yakuba.
C) descended from a single colony of D.yakuba,which had been introduced from elsewhere,with no subsequent colonization events.
D) descended from an original colony of D.yakuba,of which there are no surviving members.