Answer: C) in addition to.
Explanation: a preposition is a word governing, and usually preceding, a noun or pronoun and expressing a relation to another word or element in the clause. A compound preposition is a combination of words (for example: according to, instead of, apart from, despite of, in addition to, due to, etc). In the given sentence we can see an example of a compound preposition in the words "in addition to."
