Final answer:
The correct form of the verb 'leer' to fill the blank is 'leyó'.
Step-by-step explanation:
The correct form of the verb leer to fill the blank is leyó. The sentence translates to 'He/she read a story yesterday.' In this case, the subject 'él' (he) is singular and in the past tense, so we use the third person singular form of the verb.
Learn more about Spanish verb conjugation