Correct Answer: (7, 169)

Solution : Let's check the given options –
First option: (25, 49); 25 = 5 ² and 49 = 7 ²

Second option: (121, 169); 121 = 11 ² and 169 = 13 ²
Third option: (7, 169); 169 = 7 is not a perfect square and 169 = 13 ²
Fourth option: (9, 25); 9 = 3 ² and 25 = 5 ²

So, the third option is different from the other three options as here 7 is not a perfect square. Hence, the third option is correct.