In their very first interaction upon meeting, Miranda and Ferdinand decide to get married. When Ferdinand says "I'll make you <span>The queen of Naples", he is saying that he will marry her and she will be queen (because he assumes his father has died in the shipwreck). </span>
In this poem, Pound is comparing "faces in the crowd" to petals that are laying against a tree branch.
This is exactly what he says in the poem - "petals on a wet, black bough." A bough is the main branch of a tree, so this is definitely the only appropriate answer in this case. He wants to say that people resemble these petals.
Because people don't follow their own advice
