The most fitting answer would be C. while and however
First, the speaker is in his chamber late at night reading
his old books.
Second, the
speaker starts feeling drowsy when he hears a tapping at the window.
Third, the
speaker gets even more frightened when the curtains rustle.
Fourth, the
speaker hears a noise at the window, and a raven flies into the room.
<span>Lastly, The
speaker is surprised to find no one when he opens his door.</span>
