Question

under at an unfaltering pace,
under till the rinds break,
back till each bent leaf
is parted from its stalk;

under at a grave pace,
under till the leaves
are bent back
till they drop upon earth,
back till they are all broken

Why does the poet repeat the word "under" in these stanzas?
A)to develop conventional poetic structure
B)to emphasize the night’s impact on the flowers
C)to establish the figurative meaning of the petals
D)to describe the flowers that have fallen to the ground