A. He wants to convince readers that Buddhism is worth studying.
This is the excerpt from the preface to "Buddhism and Buddhists in China" by professor Hodous.
Professor Hodous has written this book after long years of research and missionary work in China, where he directly got familiar with their ways and philosophy, uniting in that way practical knowledge with experience.
So, the author of ths preface wanted to share with the readers some of the reasons that attracted professor to study Buddhism so deeply as well as to awake some curiosity in them to do the same.
Poe writes that Usher "entered, at some length, into what he conceived to be the nature of his malady." What exactly is his "malady" we never learn. Even Usher seems uncertain, contradictory in his description: "It was, he said, a constitutional and a family evil, and one for which he despaired to find a remedy--a mere nervous affection, he immediately added, which would undoubtedly soon pass off." The Narrator notes an "incoherence" and "inconsistency" in his old friend, but he offers little by way of scientific explanation of the condition. As a result, the line between sanity and insanity becomes blurred, which paves the way for the Narrator's own decent into madness. This madness is manifested not only in the breakdown of Usher's mind but in his decrepit body. The diseased rotting corps of his sister also illustrates this motif.
Probably foreshadowing. It doesn't seem to be a flashback or symbolism. Tone doesn't seem right -- there doesn't seem to be an easily picked out tone. So, probably foreshadowing. We all know she dies in the end, here Shakespeare's just saying "hey, she might die, just so you know"