Answer:
I think the raven (is/<u>is not</u>) real because at the end of the poem, the narrator’s state of mind is,...
There is a number of words or phrases that you could use to help smooth the transition between sentence 1 and sentence 2, and here are some of them: also, in addition, additionally, furthermore, moreover, on top of that, etc. The meaning of the second sentence adds on top of the first one - so any of these transition words would be a good choice.
