Which sentence describes how poets typically use their knowledge of sentence structure and type to create tone in poetry? They present a series of questions that guide readers to an understanding.
They directly address the reader using an implied you.
They vary the length, complexity, and mode or sentences for dramatic effect.
They use only long, complex sentences to deliver a detailed description.

They vary the length, complexity, and mode or sentences for dramatic effect.

Explanation:

When creating tone, poets will vary lengths and the complexities of sentences and will shift the mode to create emotional effects. It would not make sense for the writer to put multiple questions in a poem. Additionally, writers usually do not write when addressing the reader, but in third person. Finally, writers tend to vary their sentences to create effects on the readers. They would not purposely just use long sentences. :)

that is true because that is something they fulfill for their work.

the purpose is to inform because for some reason they really want you to know about it.