How does the metaphor in this passage most clearly support the authors purpose

Ok, so the passage and answer choices that I'm pretty sure correspond with this question is:

"For a long time, I refused to forgive Philippe for what he had said. I held on to my unforgiveness in the hopes that by drinking this poison I might kill my enemy. But soon it was my insides that were burning."

A. It illustrates unforgiveness as a poison to show how it can be administered incorrectly.

B. It compares unforgiveness as a poison to show that it hurts the offended more than the offender.

C. It likens enemies to poison to show that sometimes we don't know we've been harmed until it's too late.

D. It makes Philippe seem like poison to show how he damaged the speaker's inner being.

the answer that is correct is the last option.