The correct verb form that completes the sentence is:
D. visitaba
Explanation:
1. In the sentence, the subject "yo" (I) is singular, referring to the speaker.
2. The verb "visitaba" is in the imperfect tense, which is used to describe habitual or repeated actions in the past.
3. Since the sentence talks about a past action that the speaker did when he was young ("Cuando era pequeño" means "When I was young"), the verb "visitaba" is the correct form to use.
Therefore, the complete sentence would be:
Cuando era pequeño, yo visitaba el cementerio en el Día de los Difuntos.
