1. Which sentence does not contain any errors?

a. My two sisters doll's have unique names but both look exactly the same.

b. Our dogs and cats are not permitted to go into my Uncle Jacks' room.

c. Let's just agree, though, that my brother's room is always dirty.

d. I always try to respect everyones' opinions.

The apostrophe is only correct in sentence C

a - apostrophe belongs on sister. sister's if you are only talking about one girl who had more than one doll or sisters' if you re talking about more than one sister and there are more than one doll.

b - unless you had two uncle Jacks and they share one room, you need to put the apostrophe here: Jack's

d - everyone's opinions. Everyone has (singular) an opinion. (not everyone have an opinion)