Select the letter-cluster from among the given options that can replace the question mark (?) in the following series.
MNO, OPQ, QRS, ?
ARST
BRSP
CSTU
DTUV
ARST
BRSP
CSTU
DTUV
Related Questions:
In a certain code language,
'A : B' means 'A is the wife of B',
'A ! B' means 'A is the brother of B',
'A < B' means 'A is the son of B' and
'A / B' means 'A is the father of B'.
How is S related to E if 'S < H: A ! M / E'?