Answer:
A. It speeds up the rhythm, adding more intensity.
Step-by-step explanation:
The pace feels accelerated during the first verse of this stanza.
It is hard not to feel the intensity that this recently added rhythm brings to the poem near its end.
And the Raven, never flitting, still is sitting, still is sitting
On the pallid bust of Pallas just above my chamber door;
And his eyes have all the seeming of a demon’s that is dreaming,
And the lamp-light o’er him streaming throws his shadow on the floor;