I would say the answer is 'I'. Let me know if you got this one right.
Answer:
just be happy u ain't white!!
Explanation:
The clue word that indicates a contrast is B) However.
The writer uses the word "However" to go from describing all the similarities between coal and petroleum to describing a difference between them. When she says "<span>However, petroleum was mainly formed from the remains of ocean-dwelling microorganisms", we know that coal must have been mainly formed in a different way. The sentence that follows confirms this, stating that coal originated from dead vegetation. </span>