What is the effect of the poetic structure used in each stanza of the raven?

a. an ending rhyme scheme that repeats in the refrain gives the poem relentless tone
b. the absence of rhyme at the end of the first and third lines create a disorganized tone
c. the use of an internal rhyme scheme creates an inviting and almost playful tone
d. the ending rhyme scheme in the last three lines gives the poem a monotonous tone