1) boy's game, 1)_boys'_ games.
2)_man's_ work. 2) men's work.
3) child's piano. 3)_children's_piano.
4)_woman's_programmes. 4) women's programmes.
5) sheep's food 5)__sheep's_food
6) girl's__music 6) girls' music
7) friend's house 7)_friends'_houses