Answer: A) Separate
The word "dissever" means to separate a thing from something else. If we do not know the meaning of a word, we can sometimes guess it from the context of the sentence. In this case, the sentence states that Poe was unable to dissever himself from the grave of his wife. It is likely that the word is "separate," as grief will most likely make Poe feel as if he had to be near the grave, always.
