Question

After they were given baths, the _____ fur was soft and shiny.

A
dog's

B
dogs'

C
dogs

The two _____ plan was perfect.

A
childrens'

B
childrens

C
children's

Three of the _____ tails were injured.

A
mice's

B
mices'

C
mices

Answer 1

1. B — dogs' (plural possessive; "they" indicates more than one dog)
2. C — children's (plural "children" + 's for possession)
3. A — mice's (plural "mice" + 's for possession)