1: A. deer's
2: B. king's
3. A. books'
4. B. turtle's
For 1., we're looking for more than one deer. Since two deer left tracks, it is plural. Add the plural possessive form 's. (deer's) (You can't say "deers" even if there are more than one, the proper way is "deer". That's why the apostrophe is before the s.)
For 2., we're looking the crown of only one king, so it is singular. Add 's (king's).
For 3., we're talking about multiple books, so you add the plural possessive form s' (books').
For 4., there is one turtle, so it is singular. Add 's (turtle's).
I hope this helped! :-)
