Answer: The compound preposition in the sentence is "because of".
Explanation: Unlike a simple preposition, which consists in only one word, a compound preposition is made up of two or more words. The compound preposition in the sentence provided is "because of" because it is formed with two words: "because" and "of". Other examples of compound prepositions are "instead of", "according to", "in relation to" and "with respect to".
