Final answer:
The correct verb form to complete the sentence is 'era' which means 'was' in English.
Step-by-step explanation:
The correct verb form that completes the sentence is era. The sentence in English translates to "When I was a child, I dreamed a lot." In this case, the verb form used needs to match the subject "niño" (child) which is singular and in the past tense.
Learn more about Verb forms in Spanish