O possessive case tem seu uso na indicação de posse adicionando se um s ao dono da coisa geralmente acrescenta se o apóstrofo+ s s quando se trata de :

Araby every morning i lay on the floor in the front parlour watching her door. the blind was pulled down to within an inch of the sash so that i could not be seen. when she came out on the doorstep my heart leaped. i ran to the hall, seized my books and followed her. i kept her brown figure always in my eye and, when we came near the point at which our ways diverged, i quickened my pace and passed her. this happened morning after morning. i had never spoken to her, except for a few casual words, and yet her name was like a summons to all my foolish blood. what is the general tone of the passage? a. courageous b. comical c. passionate d. fearful