Final answer:
The imperfect form of the verb "leía" in the sentence "El niño leía el libro" is correct.
Step-by-step explanation:
The sentence "El niño leía el libro" is correct with the imperfect form of the verb. The imperfect tense is used to describe ongoing or repeated actions in the past, or to set the background for another action. In this sentence, the verb "leía" indicates that the child was reading the book continuously or repeatedly in the past. It shows an ongoing action in the past.
Learn more about Imperfect tense in Spanish