Homologous structures such as the bones in wings, flippers, and arms are most closely concerned with

Homologous structures are mostly concerned with "COMPARATIVE ANATOMY"

Explanation:

Homologous structures are body parts that appears similar based on their connection and location suggesting their connection to a common ancestor. These structures do not have to look exactly the same, or have the same function, but it appears similar in different organism, in this case wings, flippers and arms share similarities.

Hence the comparative anatomy theory which is concerned with exploring and establishing these similarities of body structures (Homologous structures) of different animals/organism. The purpose of this is to understand the adaptive changes developed during the course of evolution especially from related ancestral lineage.

i think the answer would be d

chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation: