A scientist tries to mate the two similar-looking fruit flies Drosophila melanogaster and Drosophila simulans. He finds that they are unable to produce viable offspring. What kind of evolutionary barrier could this be?

A. Chromosomal

B. Postzygotic

C. Physical

A Drosphila melanogaster and a Drosphila simulans are unable to produce viable offspring because of (B) Postzygotic evolutionary barrier. This is because the hybrid of the two cannot regularly form their genes together. When this does happen, the offspring generally does not live because the baby cannot mature enough and it usually dies before being born.