If the item owned is plural, your possessive adjective be plural. Example: "My book" →right arrow Mi libro. Example: "My books" →right arrow Mis libros. Step 3: Handle the Ambiguity of "Su" and "Sus"
In Spanish, you cannot end a sentence with a preposition. Instead of saying "Whose book is this?", the structure translates literally to "Of whom is the book?". p219 estructura 1 de quien es practice it upd