Answer:
Your answer would be that "watching a scary film with my friends at the theater" is a sentence fragment.
Step-by-step explanation:
"Watching a scary film with my friends at the theater" is a sentence fragment. Sentece fragments are groups of words that look like sentence, but aren't. To be a sentence, groups of words need to have at least one independent clause. An independent clause is any group of words that contain both a subject and a verb and can stand on its own as a sentence because it represents a complete thought. In this case, the sentence fragment fails to stand on its own because it does not represent a complete thought. It contains neither a subject nor a predicate (see 1) as opposed to the other sentences which are independent clauses (2 & 3).
1) *Watching a scary film with my friends at the theater
2) Call me
3) If you do not understand, ask your teacher for help