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

Correct option is B

From the given options –
(a) 19 : 361 → 19² = 361
(b) 23 : 539 → 23² = 529 ≠ 539
(c) 28 : 784 → 28² = 784
(d) 17 : 289 → 17² = 289
In all options except (b), the second number is the square of the first number. However, in option (b), 539 is not the square of 23, making it the odd one out.
Therefore, the correct answer is (b) 23 : 539.