In my opinion, the correct answer is B: "fades from my sight". The speaker couldn't even hold on to that sight. The uncle's talk doesn't seem to comfort him at all - only the picture of the grave is in his mind, even though he could only look at it in passing. He feels not only sad but also isolated, as he finds no comfort in the outside world. Also, this phrase is repeated twice, as if to signify the speaker's obsession with the scene.
