The correct option is C 15
A fraction is in its simplest form when the numerator and denominator cannot be any made any smaller by dividing both by the same number.
Now, dividing both numerator and denominator of 25125 by 5, we get 25125=525
But, this can be simplified even further. As both the numerator and denominator are still divisible by 5.
Dividing both numerator and denominator of 525 by 5 again, we get 525=15
So, 15 is the simplest form of the fraction 25125 as it cannot be reduced further.