Series : CAL, AWF, YSZ, WOT, ? The pattern followed in each letter of the terms is : 1st letter : C (-2 letters) = A (-2 letters) = Y (-2 letters) = W (-2 letters) = U 2nd letter : A (-4 letters) = W (-4 letters) = S (-4 letters) = O (-4 letters) = K 3rd letter : L (-6 letters) = F (-6 letters) = Z (-6 letters) = T (-6 letters) = N Thus, missing term = UKN