Which clarifying sentence is most relevant to the information in the passage?
corals are anthozoans—the largest class of organisms within the phylum cnidaria.
a volcanic island is formed on layers of solidified lava from an undersea volcano.
fringing and barrier reefs can be thought of as stages in the formation of atoll reefs.
zooxanthella algae are critical elements in the continuing health of reef- building corals.

Fine fellow, that lebrun," said arobin when robert had gone. "i never heard you speak of him.""i knew him last summer at grand isle," she replied.  what becomes apparent during this conversation? robert and arobin are both aware they are rivals for edna’s affections.arobin is unaware of robert’s role in edna’s life, but robert is aware of arobin’s role.robert is completely unaware of arobin’s romantic intentions and love for edna.robert has much more confidence in himself than arobin does.