Question

which of the following means once upon a time?
de repente
hace muchos siglos
había una vez

Explanation:

"Once upon a time" is a common phrase used to start a story. In Spanish, "Había una vez" is the equivalent phrase used to begin a story, just like "Once upon a time" in English. "De repente" means "suddenly" and "Hace muchos siglos" means "many centuries ago".

Answer:

Había una vez