Read these lines from Edgar Allan Poe's "The Raven": " 'Tis some visitor entreating entrance at my chamber door. Some late visitor entreating entrance at my chamber door."

a) Describe the speaker's emotions upon hearing the visitor.
b) Analyze the use of repetition in the lines.
c) Explain the significance of the visitor's arrival.
d) Explore the mood created by the description of the chamber door.