The boys shoes (1 boy)

1.   ?    The boys shoes
2.   ?    The boy's shoes

The womens room

1.   ?    The womens' room
2.   ?    The women's room

I havent a clue

1.   ?    I have'nt a clue
2.   ?    I haven't a clue

The ladies toilet

1.   ?    The ladies' toilet
2.   ?    The ladie's toilet

Its too difficult.

1.   ?    Its too difficult.
2.   ?    It's too difficult.

The childrens father

1.   ?    The childrens father
2.   ?    The children's father

The girls work (5 girls)

1.   ?    The girl's work
2.   ?    The girls' work

The rabbits hutch (3 rabbits)

1.   ?    The rabbits' hutch
2.   ?    The rabbit's hutch

He doesnt like you

1.   ?    He doesn't like you
2.   ?    He does'nt like you

I don't like its pattern.

1.   ?    I don't like its pattern.
2.   ?    I don't like it's pattern.

The cats whiskers (1 cat)

1.   ?    The cat's whiskers
2.   ?    The cats' whiskers

Carrots are good for you

1.   ?    Carrots are good for you
2.   ?    Carrot's are good for you

The mens work

1.   ?    The men's work
2.   ?    The mens' work

The dolphins pool (4 dolphins)

1.   ?    The dolphin's pool
2.   ?    The dolphins' pool

The doctors wife

1.   ?    The doctor's wife
2.   ?    The doctors' wife

The dogs dinner (1 dog)

1.   ?    The dog's dinner
2.   ?    The dogs' dinner