Before the Cultivation of the Apple Tree,apple Maggot Flies Laid

Before the cultivation of the apple tree,apple maggot flies laid their eggs exclusively on the fruit of Hawthorne trees.As apple orchards became more prominent,apple maggot flies began to lay their eggs on both the fruit of the Hawthorne tree and the fruit of cultivated apple trees.Now,apple maggot flies that live on apple trees mate and lay their eggs at different times of the year than apple maggot flies that live on Hawthorne trees.Is this an example of reproductive isolation?

A) Yes; these two fly populations exhibit a postzygotic barrier that prevents hybrid individuals from developing properly.
B) No; although these two fly populations do not mate in nature, they can be forced to mate in a laboratory because their DNA sequences are still the same.
C) No; this is an example of speciation rather than reproductive isolation.
D) Yes; these two fly populations exhibit a temporal prezygotic barrier that prevents their gametes from encountering each other.