What organ is able to extract dissolved oxygen from water?

The organ that living things such as fish use to extract dissolved oxygen from water are the gills. As land animals and humans don't have gills, we can't breath underwater and take in the oxygen from that source.

Fish, sea slugs, and all underwater animals have organs called gills which allow them to extract dissolved oxygen from the water and therefore 'breathe' and live underwater.

The answer is b, as with an inference you make a statement with no evidence