The pattern is as follows: The first and last element of each group is a series of alternate letters in the alphabetical order. A + 2 = C, C + 2 = E, E + 2 = G, G + 2 = I, I + 2 = K, K + 2 = M, M + 2 = O, O + 2 = Q, Q + 2 = S, S + 2 = U, U + 2 = W The next number is two times the last number. 2 × 2 = 4, 4 × 2 = 8, 8 × 2 = 16, 16 × 2 = 32, 32 × 2 = 64 Hence, “U64W” is the correct answer.