Answer:
Leyó
Step-by-step explanation:
So the sentence has a verb that was performed by the teacher, in past, so taht would be a verb perfomed and conjugated for the third person in the past, oyó and leyó are verbs conjugated in the third person in past, the difference is that leyó is read, and oyó is heard, and since the sentence is speaking about a book, leyó would be the best answer, that would be your correct answer.