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.

4209 : 15 5121 : 12 8101 : 10 7456 : 22

5121 : 12

he logic followed here Is : Sum of the digits in ist number = second number 4209 : 15 4 + 2 + 0 + 9  = 15 5121 : 12 5 + 1 + 2 + 1 = 9 (odd) 8101 : 10 8 + 1  + 0 + 1 = 10 7456 : 22 7 + 4 + 5 + 6 = 22