In the sentence " I just love raking the yard in the fall. I especially love the painful blisters and the aching back I get when I'm raking," the sarcastic word is LOVE. Option A is correct.
In this sentence "love" is sarcastic because the speaker actually refers to the contrary. He does not love to neither to rake nor the aching back he suffers when raking.
Sarcasm can be defined as the use of remarks that clearly mean the opposite of what they say, made in order to hurt someone's feelings or to criticize something in a humorous way.