CDE, IJK, NOP, ?
From Alphabet Series · Verbal Reasoning
A, D, H, M, ?, Z
ACE, GJI, MQM, ?
DWEV, FUGT, HSIR, ?
AZ, CX, FU, ?
T, R, P, N, L, ?, ?
ZCBA, YFED, XIHG, ?
ADGJ, YVSP, KNQT, ?
Y, S, U, O, Q, ??