IN WHICH OF THE FOLLOWING SENTENCES IS THE POSSESIVE USED CORRECTLY?

A. The boy's basketball team plays every
Friday, but the girls play every other Thursday.
B.Their's is the first bus to arrive at school every morning.
C. The childrens' activity period lasts 15 minutes.
D. Carl's and Sara's schoolbooks are on the kitchen table.

I think the answer is A
Am I correct

D is correct.

It is not A because "boys" is plural (referring to a whole team), so the apostrophe in that case comes after the s. One boy does not own the team.