I would say the best answer is A. Answer choice B is rather absurd and answer choice C doesn't exactly make any sense.
Answer:
Why did Phillis Wheatley write "On Being Brought from Africa to America"? to describe the horrors of slave ships to tell what it was like in her native land to emphasize that blacks may become Christians to encourage people to bring Africans to America
Explanation:
This depends on the sentence given. Prepositions are words that associate an object to a certain location or position. Examples of prepositions are: on, after, below, by, during, and many more. If you want to use the word 'opportunities' as the object of your preposition, an example would be as follows:
Mary is hopefully praying for good luck as she takes on opportunities. The preposition is 'on' and the object of preposition is 'opportunities'.