The correct answer is A.) Prepositional phrase
Assuming that in the last option 'whichever melody you create' is underlined, the correct answer is that one, the last sentence. Because this is the only sentence in which 'to' is used as a preposition, in 2 and 3 there are no prepositions, and in 1 'to' is a part of an infinitive phrase.
Romeo's parents are Montague and his wife. Hope this helps!