A parallel sentence mentions the same grammatical expression twice. I would go with "D". 'Passed' and 'Demonstrated' are both past tense words that express the same past tense grammatical idea.
If you have more questions, feel free to ask me.
Secrets are one of the central themes in the book, although they are not the most prominent theme, they are quite important, as the ending of the book relies heavily on an untrue fact and untrue story, or rather a secret, which determines the fate of one of the characters. This quote (above in your question) particularly mirrors the quote " You never really know a person until you consider things from his point of view...until you climb into his skin and walk around it." Boo Radley remains a secret from the beginning of the book until the end and this quote relates to him as Scout and Jem try to figure him out, since he is so mysterious, yet another one of the secrets present in the novel.
He used magic to make it look like a dream like state in the red death and the tone helped create expression in the poem
