The Answer would be Estar
Idk if you have specific vocab but if you can put anything just pick something bigger than a book.
No sé si tiene vocabulario específico, pero puede usar cualquier cosa que sea más grande que un libro.
Elefante, cama, casa, gato, etc.
Answer: its son beacuse es woudnt make sense in that sentence
Explanation: think about it quienes it wouldnt go with es bc the end of quienes is es. It would only make sense with son. its kinda hard to explain. ig since im hispanic and ive hurd and used that word before. I cant really explain it that well sory but i hope this somewhat helped but trust mi its son .
