Step 1: Identifying the pattern

Observing the letter clusters, we see that:

RTTUWW → Contains repeated pairs: TT, UU, WW

ACCDFF → Contains repeated pairs: CC, DD, FF

IKKLNN → Contains repeated pairs: KK, LL, NN

NOPPSS → Contains repeated pairs: PP, SS

All clusters contain three pairs of repeated letters.

Step 2: Finding the odd one

If we check the sequence in the alphabetical order:

RTTUWW → (R, T, T, U, W, W)

ACCDFF → (A, C, C, D, F, F)

IKKLNN → (I, K, K, L, N, N)

NOPPSS → (N, O, P, P, S, S)

The first three clusters follow a pattern where the repeated letters are in a structured, non-consecutive pattern, while NOPPSS does not follow the same pattern strictly.

Conclusion:

NOPPSS (Option 2) is the odd one out ✅ because its letter arrangement does not follow the same increasing structured pattern as the others.

The correct answer is Option 2: NOPPSS.