Respuesta :
After my grandparents sent me a book about aeronautics, I wrote them a thank-you note
Indirect object refers to whom or for whom the action is being done. It is a prepositional phrase in which the prepositions, for or to is understood without stating it. Also, the indirect object is placed between the verb and the direct object.
Therefore, the sentence which uses the indirect object is "After my grandparents sent me a book about aeronautics, I wrote them a thank-you note."
Herein, the verb is 'sent' and the direct object is 'a book', and between is, the direct object 'me' in which preposition 'to' is understood without its placement.