Answer:
In the structure "Bothered by a sore back, Houston decided to spend the day in bed", the segment "bothered by a sore back" is a participial phrase.
Explanation:
A participial phrase functions as an adjective, modifying the noun. In the structure we are studying here, the participial phrase "bothered by a sore back" is modifying the proper noun Houston, giving us extra information about that person. A participial phrase always starts with the participle form of a verb - "bothered", in this case.
A noun sentence would function as a subject or an object in a sentence.
A prepositional phrase consists of preposition and its object.
An infinitive phrase starts with the infinitive form of a verb.
