Which of the following letter-number-clusters will replace the question mark (?) in the given series to make it logically complete?
VRO 6, UQN 11, TPM 16, SOL 21, ?​

VRO 6, UQN 11, TPM 16, SOL 21, ?​

Logic: Each letter - 1, Number + 5

V -1 → U, U -1 → T, T -1 → S, S -1 → R
R -1 → Q, Q -1 → P, P -1 → O, O -1 → N
O -1 → N, N -1 → M, M -1 → L, L -1 → K
6 +5 → 11, 11 +5 → 16, 16 +5 → 21, 21 +5 → 26

So, RNK 26 is missing term.

Thus, correct option is (c).