Answer: C. lo presté
Juan: ¿Tienes el libro de historia?
Ricardo: No, lo presté a Mariana.
Juan: Do you have the history book?
Ricardo: No, I lent it to Mariana.
Explanation: The direct object of the verb "prestar" is "el libro", this is a plural masculine noun, therefore its direct object pronoun has to agree in gender and number with the noun it replaces. "Lo presté"
Spymore