The Sugar Glider in Australia and the Flying Squirrel in North

The sugar glider in Australia and the flying squirrel in North America are both small mammals with large expanses of loose skin between their forelimbs and hindlimbs, allowing them to glide from tree to tree within their respective forest habitats. These two species are not evolutionarily related but are very similar in their overall appearance. Darwin's explanation for their similarity is that

A) both are descendants from a recent common ancestor.
B) each have adapted in very similar ways to similar habitats.
C) the similarity of the two unrelated species is simply coincidence.
D) the two species were created to have similarities.
E) the two species must be related to possess such like qualities.