Four number-pairs have been given, out of which three are alike in some manner and one is different. Select the one that is different.

From the given Option (B), (C),(D) is follow the same pattern given below

(B) 64: 100 it is perfect square 8 and 10 

(C)25:36 it is a perfect square of 5 and 6

(D)16:49 it is also a perfect square of 4 and 7

But Option (A) does not follow the perfect square pair 

(A) 48: 81  where 48 is not a perfect square and 9 is a perfect square of 81

therefore (A) 48:81 is different from the given option

Ans (A) 48:81