Answer:
Complete sentence
Step-by-step explanation:
Every sentence must contain a subject and a predicate and express a complete thought. The given group of words contains all of these elements, which is why it can be defined as a sentence. Which is the complete subject, was the best part of the movie is the complete predicate, and all of the words together make up a sentence that makes sense and is complete.
A sentence fragment is a group of words that resembles a sentence but isn't actually one because it lacks at least one of the elements listed above (subject, predicate, or complete thought).
A run-on sentence is a sentence that consists of incorrectly connected independent clauses.