Correct option is A
Given: DNY, YIT, TDO, OYJ, ?

Logic: Each letter - 5 position
1st letters: D - 5 → Y, Y - 5 → T, T - 5 → O, O - 5 → J
2nd letters: N - 5 → I, I - 5 → D, D + 21 → Y, Y - 5 → T
3rd letters: Y - 5 → T, T - 5 → O, O - 5 → J, J - 5 → E
Missing term: JTE
Thus, correct option is (a).