Series : COT, DQU, ESV, FUW, ? The pattern followed in each letter of the terms is : 1st letter : C (+1 letter) = D (+1 letter) = E (+1 letter) = F (+1 letter) = G 2nd letter : O (+2 letters) = Q (+2 letters) = S (+2 letters) = U (+2 letters) = W 3rd letter : T (+1 letter) = U (+1 letter) = V (+1 letter) = W (+1 letter) = X Thus, missing term = GWX