Answer:
No change is to be made in sentence 25.
Step-by-step explanation:
This is the correct answer because the first one isn't even proper. The second one can't be changed to a period because then it's not a full sentence and the comma is there to give this sentence a pause. and the last one, you would say it's if you are saying it is, but "its" is used perfectly in this sentence the way it is.