Final answer:
The imperfect form of the verb in the sentence is correct.
Step-by-step explanation:
The subject of this question is Spanish and the grade level is High School.
The sentence in question is: El niño leía el libro. The imperfect form of the verb in this sentence, which is leía, is correct. In Spanish, the imperfect tense is used to describe ongoing actions in the past, habits, or to set the background of a story. In this sentence, it indicates that the child used to read the book or was reading the book in the past.
Learn more about Imperfect form of verbs in Spanish