Final answer:
The 'imperfecto' in Spanish is used to talk about past actions or events that were ongoing, habitual, or repeated in the past.
Step-by-step explanation:
The correct option that uses the 'imperfecto' in Spanish is: I used to go to the gym. The imperfect tense, or 'imperfecto' in Spanish, is used to talk about past actions or events that were ongoing, habitual, or repeated in the past. In this case, going to the gym was a regular and repeated action in the past. The other options use different tenses: the simple past tense (went) and the past perfect tense (ate).
Learn more about The use of the 'imperfecto' in Spanish