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