The first letters are in alphabetical order with a letter skipped in between each segment: C, E, G, I, K. The second and third letters are repeated; they are also in order with a skipped letter: M, O, Q, S, U.
This justifies what answer for what question? Q & A: 
CMM, EOO, GQQ, _____, KUU
Options:
(A) MSQ
(B) IPS
(C) IIS
(D) ISS
(E) POL
(D)