The correct answer is B. the pattern of end rhymes. In poetry, the rhyme scheme refers to the pattern of rhymes at the end of each line of a poem. Here is an example form Roberts Frost's poem "Neither Out Far Nor In Deep":
The people along the sand (A)
All turn and look one way (B)
They turn their back on the land (A)
They look at the sea all day (B)
The uppercase letters at the end of each line denote the rhyme. The rhyme scheme in the poem above would be ABAB because line 1 rhymes with line 3 and line 2 with line 4.
