Question

¿pretérito o imperfecto? acción principal en una historia; el imperfecto; el pretérito

Explanation:

In Spanish, the pretérito is used for actions that are completed (the main actions in a story, as they are specific, single - event actions). The imperfecto is used for background, ongoing, or habitual actions. Since the question is about the main action in a story, the pretérito is the correct tense.

Answer:

el pretérito