There is one prepositional phrase in the sentence.
Answer: Option C.
Step-by-step explanation:
A prepositional phrase is the one which contains a preposition, its objects, and the modifier regarding the same. Some most common prepositions are: at, by, for, in, on, from, under, with, to, over, during. In the sentence, "Ursula decided that she wanted a new bicycle for her birthday because her current bicycle needed some repairs", there is one preposition which is, 'for.' And thus the prepositional phrase in this sentence is 'for her birthday.'