Hi Tyler. Your example phrase is a fragment of a sentence. It lacks the subject saying "who" is decorating for the party, One of the simplest ways to determine if a phrase is a sentence is to ask yourself if it's a complete thought. Is anything unclear about the phrase? You could complete the phrase in many ways. For example, I decorated the house for the party. (singular pronoun) We decorated the house for the party. (plural pronoun) These examples answer the question of "who" is decorating the house. Either example creates a complete sentence.
"Decorating the house for the party"
