This metaphor meant that they climbed and jumped rock to rock sure-footed
A. Complacent he is sure he is fine
In this poem, the author describes the "music" that the movement of the black girl brings to our ears. He talks about the way in which the girl's playing makes her braids move, and he describes this musicality by using words such as "symphony","crescendo", and "movement." These words are employed as imagery, and their effect is that they create an image in the mind of the reader. This image contributes to the meaning of the poem by portraying the vivacity and cheerfulness of the girl.
To be reticent is to not reveal one's thoughts readily. In this case, it is the reticence of the author. The author does not reveal their thoughts readily. If the narrator or author refuses to do something, it is made known that he is doing something. The something here is him refusing. If he acts as if the situation is normal, I'd assume he is acting in such a way that would be nonreactionary of the actions from the provoker. I would safely choose the last option as sorrentino's exercising of authorial reticence.