Answer: C. Kelly's dog has spots all over its body
Step-by-step explanation:
A. We have been studying the moon and it's phases.
This is wrong. It should be:
We have been studying the moon and its phases.
B. Your science report is much longer than our's.
This is wrong. It should be:
Your science report is much longer than ours.
C. Kelly's dog has spots all over its body.
This is punctuated correctly.
D. This globe is your's to keep!
This is wrong. It should be:
This globe is yours to keep!
Therefore, the correct option is C.