He was not surprised because he was already going insane. Since he was hallucinating that the raven was spouting words at him. He was already ill to begin with so it was not a surprise he thought the raven spoke.
Honestly, I doubt a teacher can even give an actual grade for these because these are extremely debatable to people and are more useful just for psychiatric testing.
If you feel that your answer works, you can always right next to it and explain your reasoning!
