Correct Answer: ET

Solution : Let's check the options –
First option: AG; A (1) + G (7) = 7 + 1 = 8 (This is an even number.)
Second option: WA; W (23) + A (1) = 23 + 1 = 24 (This is an even number.)
Third option: ET; E (5) + T (20) = 20 + 5 = 25 (This is an odd number.)
Fourth option: IQ; I (9) + Q (17) = 9 + 17 = 26 (This is an even number.)

So, the third option is different from the other options as the resultant is an odd number. Hence, the third option is correct.