Two Hundred Years Ago, the Fly Species Rhagoletis Pomonella Only

Two hundred years ago, the fly species Rhagoletis pomonella only laid its eggs on fruit of the hawthorn tree. Today, different "host races" of R. pomonella lay their eggs on hawthorns OR apples. Apples occur within the range of hawthorns, so divergence between apple flies and hawthorn flies could be the first step in sympatric speciation. Choose the evidence that supports that R. pomonella is undergoing sympatric speciation. Check all that apply.

A) Apple flies typically mate with apple flies, and hawthorn flies typically mate with hawthorn flies.
B) Apple flies and hawthorn flies emerge from their hosts at different times of the year.
C) Apple flies and hawthorn flies are able to form fertile hybrids.
D) Apple flies and hawthorn flies are physically indistinguishable from each other.