A <em>prepositional phrase </em>refers to the phrase which begins with a preposition and ends with the 'objects' of the prepositions that are nouns, gerund, clause or pronoun.
The pattern of the <em>prepositional phrase</em> follows by the object of the preposition having one or more modifiers.
Therefore, in the above sentence, the prepositional phrase is C. down the street.
<em>'down'</em> is a preposition followed by the modifier <em>'the street'</em> as a noun.
