Question

I was just wondering if one of you would be willing to check my answer on this question:

Read this line from The Fall of the House of Usher:

Shaking off from my spirit what must have been a dream, I scanned more narrowly the real aspect of the building.

The author's emphasis on the word "must" in this line suggests which of the following about the narrator?

He cannot distinguish dream from reality****

He has little experience with dream-like states.

He is not certain it was a dream at all.

He still wants to be in a dream.