Answer: C) Because of.
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 prepositions are those which are formed by prefixing the preposition to a noun, an adjective or an adverb. In the given sentence we can see an example of a compound preposition in the words "because of" (corresponding to option C).
