Explanation:

Let's analyze the patterns in the given series:

- KTY, NXD, QBI, TFN, ?

- Observe the pattern in each character position:

- The first letters: K, N, Q, T. These progress by +3 in the alphabet: K(11)+3=N(14), N(14)+3=Q(17), Q(17)+3=T(20), thus next is T(20)+3=W(23).

- The second letters: T, X, B, F. These progress by +4: T(20)+4=X(24), X(24)+4=B(2, consider loop around alphabet)=B, B(2)+4=F(6), thus next is F(6)+4=J(10).

- The third letters: Y, D, I, N. These progress by +5: Y(25)+5=D(4, wrap around)=D, D(4)+5=I(9), I(9)+5=N(14), thus next is N(14)+5=S(19).

- So, the letter cluster that fits this sequence is WJS.

- Correct Answer: Option 2 ? WJS