Final answer:
The correct answer is option d. Feathers are an example of exaptation, as they originally evolved for some other function and later became adapted for flight in convergent evolution. The wings of bats and insects are another example of convergent evolution, where the structures evolved independently for flight.
Step-by-step explanation:
Feathers are an example of a/an exaptation; they originally evolved for some other function and only later became adapted for flight. This is known as convergent evolution, where similar traits evolve independently in species that do not share a common ancestry.
In the case of feathers, they likely originated for insulation or display purposes and later became adapted for flight. The wings of bats and insects are another example of convergent evolution, where the structures evolved independently to enable flight in these two distantly related species.