The verb is "exist." The simple subject is the word that tells what exists.
I'll be glad to check your answer.
Note the prepositional phrase. Subjects and verbs are never in prepositional phrases.
What is the simple subject of ,Many stories about the first Valentine's Day exist?
4 answers
The complete subject is, Many stories about the first Valentine's day. The simple subject is stories.
Right.
What do Many stories about the first valentine's Day exist