What element of a written work best determines if the work is sarcastic or
not?
O
A. Symbolism
O
B. Format
O
O
C. Context
D. Conflict

I actually read this poem upon reading your question, And I can conclude that it would be "Blue as blood on his left forearm"

You see, he is speaking of the numbers that were put on his fathers arm between his wrist and forearm as a numbering system.