Possessive Case: 's or s' ?

Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!

a) bag is under the chair. (Ann)
b) My books are in the bag. (my brothers)
c) Where is your coat? (your sister)
d) That´s my house. (my parents)
e) I don´t know my address. (my friend)