Find the missing term in the following series:
UPI, ?, ODP, MBQ, IAW
[A]RHJ
[B]SHJ
[C]SIJ
[D]THK

SHJ
In the above question, the pattern is,
1st letter
$latex Y\xrightarrow{\text{-2}}\textcircled{S} \xrightarrow{\text{-4}}O \xrightarrow{\text{-2}}M \xrightarrow{\text{-4}}I $
2nd letter
$latex P\xrightarrow{\text{-8}}\textcircled{H} \xrightarrow{\text{-4}}D \xrightarrow{\text{-2}}B \xrightarrow{\text{-1}}A $
3rd letter
$latex I\xrightarrow{\text{+1}}\textcircled{J} \xrightarrow{\text{+6}}P \xrightarrow{\text{+1}}Q \xrightarrow{\text{+6}}W $