Answer:
the answer is VY
Explanation:
Between each pair of letters there is 1 missing letter, between each letter in a pair there are 2 missing letters.
I've denoted the missing letters with parentheses:
(A) B(CD)E
(F) G(HI)J
(K) L(MN)O
(P) Q(RS)T
(U) V(WX)Y