Find the missing term in the following series:
DEF, HIJ, MNO, ?
[A]STU
[B]RST
[C]RTV
[D]SRQ

STU
In the above question, the pattern is,
1st letter
$latex D\xrightarrow{\text{+4}} H \xrightarrow{\text{+5}} M \xrightarrow{\text{+6}}\textcircled{S} $
2nd letter
$latex E\xrightarrow{\text{+4}} I \xrightarrow{\text{+5}} N \xrightarrow{\text{+6}}\textcircled{T} $
3rd letter
$latex F\xrightarrow{\text{+4}}J \xrightarrow{\text{+5}} O \xrightarrow{\text{+6}}\textcircled{U} $