The second number in the given number-pairs is obtained by performing certain mathematical operation(s) on the first number. The same operation(s) is/are followed in all the number-pairs, except one. Find that odd number-pair.
(NOTE: The relation should be found without breaking down the numbers into its constituent digits)

Correct option is A

Concept:
All except option a follow the same pattern.
19² : 20², 23² : 24², 21² : 22²
the second number is obtained by squaring the next integer after the integer whose square gives the first number (i.e., (n+1)²).
Explanation:
225:169
225 is the square of 15.
169 is the square of 13.
361:400
361 is the square of 19.
400 is the square of 20.
529:576
529 is the square of 23.
576 is the square of 24.
441:484
441 is the square of 21.
484 is the square of 22.
From the analysis, we can see:
In pairs (b), (c), and (d), the second number is obtained by squaring the next integer after the integer whose square gives the first number (i.e., (n+1)²).
In pair (a), both numbers are squares of two integers, but they do not follow the same pattern of consecutive squares.
Therefore, the odd number-pair is (a) 225:169.