Please check this Apostrophe:

Question

1) Kates' sister
2) the giraffe's neck
3) the parent's anniversary
4)the senator's cars
5) Toms' folder
6) the deer's habitat

Answer 1

1. no
2. yes
3. only if there's one parent
4. only if there's one senator
5. no
6. yes

Answer 2

http://www.chompchomp.com/terms/apostrophe.htm

Answer 3

Half of them are right.

http://grammar.yourdictionary.com/parts-of-speech/nouns/Possessive-Nouns.html