By telling "I’ve known rivers," the author mentions that he has seen the rivers in the past. Known also means that the speaker knows the rivers for quite some time that he passed his time there and made himself acquaintance with the rivers. By saying "I've known rivers ancient as the world and older than the...", the author begins to describe the features if the rivers and completing the sentence with "...flow of human blood in human veins" he shows that those rivers are even older than the blood that gives life to humans. The lines cast light to the history of Black Lives. They show that the Black history is very old in reality.
The structure of the poem looks like:
I’ve known rivers:
I’ve known rivers ancient as the world and older than the flow of human blood in human veins.
My soul has grown deep like the rivers.
We cannot say that there is a variation of meter because "veins" and "rivers" are not rhyming in this context. In this logic we cannot apply the answers with stanzas. Therefore, the last option is the correct one - D) nontraditional syntax and rhyme scheme.
