A series is given with one term missing. Select the correct alternative from…

Solution:

Look at each letter column separately and find the step applied down the series.

• 1st column: T → W → Z → ? → F. Pattern: add 3 each time (wrap after Z). Z + 3 → C. So 1st letter = C.

• 2nd column: O → T → Y → ? → I. Pattern: add 5 each time (wrap after Z). Y + 5 → D. So 2nd letter = D.

• 3rd column: N → G → Z → ? → L. Pattern: subtract 7 each time (equivalently add 19). Z − 7 → S. So 3rd letter = S.

• 4th column: Y → P → G → ? → O. Pattern: subtract 9 each time. G − 9 → X (wrap). So 4th letter = X.

Combining the letters gives the missing term CDSX, which matches the correct choice CDSX.