Answer:
Prepositional Phrase - along the low wall
Subject - You
Verb - sit
D.O. - The low wall.
Step-by-step explanation:
Prepositional phrases are characterized as the phrases that consist of a preposition followed by its object or complement and function primarily as an adjunct or modifier of the noun or verb to add detail to the sentence. While the subject is the one who performs the action in the sentence. Since the sentence is imperative(begins with a verb), the subject(implied) would be 'you.' Verb is the primary action performed by the subject i.e. 'sit' and the direct object is that which directly receives the action performed by the subject i.e. 'the low wall.'