What should come in place of the question (?) in the given series based on the English alphabetical order?
IGK, LJN, OMQ, RPT, ?

IGK, LJN, OMQ, RPT, ?

Logic: Each letter getting +3 

First letters:
I + 3 = L
L + 3 = O
O + 3 = R
R + 3 = U

Second letters:
G + 3 = J
J + 3 = M
M + 3 = P
P + 3 = S

Third letters:
K + 3 = N
N + 3 = Q
Q + 3 = T
T + 3 = W

Next term: USW