Final answer:
The fins of fish have skeletal and muscular structures similar to amphibian limbs. This is an example of homologous structures.
Step-by-step explanation:
The subject of this question is Biology, and it is suitable for High School level students.
The correct answer is a) Fish. The fins of fish have skeletal and muscular structures similar to amphibian limbs. This is an example of homologous structures, as the similarities between fish fins and amphibian limbs can be attributed to a common evolutionary history.
For example, the fins of Sarcopterygii, a group of fish, are fleshy and lobed, supported by bones that resemble the limbs of early tetrapods like amphibians.