The scientific name for a white oak is quercia alba; the scientific name for a red oak is quercia ribera what does this tell you about the organism?

The scientific name for white oak is Quercia Alba and the scientific name for red oak is Quercia Ribera, this tells us that both the species are closely associated because of the fact that they are in the similar genus. A genus refers to a principal taxonomic category, which ranks below family and above species, and is signified by a capitalized Latin name.  

This also suggests that all of their taxonomic groups are similar from domain to genus. The more common taxonomic groups exhibited by the organisms, the more closely they are associated.  

it is called an accent mark

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."