Answer:
2). A group of words that work together as a unit.
Step-by-step explanation:
A phrase is usually described as a group of two or more words that works together as a unit and able to communicate something meaningful. However, phrases fail to offer a complete thought due to the absence of a subject and verb. The phrases work as a part(not whole) of a sentence or clause in order to accomplish its meaning(as a noun, adjectives, or adverbs) and add content to the sentence(as subject(through noun phrase), as a subject complement(through prepositional phrase), etc.). Thus, option 2 best defines a phrase as 'a group of words that works together as a unit'.