The sentences that cointains a prepositional phrase from the examples given are:
A. You may think otherwise, but what I tell you is true.
B. Where did you find the papers that I lost?
A prepositional phrase is a group of words that begins with a preposition and ends in a noun, a pronoun or a nominal phrase (the object of the preposition). The prepositional phrases give us more information about the word (s) they describe
Americans are also unlikely to put individual happiness before the institution of marriage — they were second most likely (after the British) to agree that even a childless couple should “stay together even if they don’t get along.”