Choose the odd one out from the following:

Correct option is A

Logic: difference of position value of two letters - 1 = last number
JR6 => 18 - 10 - 1 = 7 ≠ 6
RV3 => 22 - 18 - 1 = 3
EK5 => 11 - 5 - 1 = 5
DG2 => 7 - 4 - 1 = 2
So, JR6 is the odd one out as shown above.