Y, S, U, O, Q, ??
From Alphabet Series · Verbal Reasoning
CDE, IJK, NOP, ?
BMO, EOQ, HQS, ?,
ACE, GJI, MQM, ?
A, D, H, M, ?, Z
T, R, P, N, L, ?, ?
AZ, CX, FU, ?
PRQ , TVU , YAZ , ?
QYK, ?, ISG, EPE