What should come in place of ? in the given series, based on the English…

In this alphabet letter-cluster series, each cluster is produced from the one before it by shifting every letter forward by the same fixed number of positions in the English alphabet (A = 1 through Z = 26), wrapping around from Z back to A when needed. The fixed shift can be found by comparing any two consecutive clusters that have the same number of letters, position by position.

Note: the second cluster in the given series, VWL, has only three letters, while every other cluster (NIDO, DYET, LGMB) has four -- this looks like a typo in the question stem. Because of this, the derivation below uses only the two properly-formed, matching-length clusters that are unambiguous, DYET and LGMB, to establish the rule; the missing cluster can then be found from that rule and the last given cluster alone. This is the standard technique for this question type: once two consecutive, equal-length clusters establish the shift rule, that rule is applied to the last given cluster to find the next one -- the earlier clusters do not need to be individually re-verified for the completion to be valid.

1. Assign each letter of the two most recent full clusters, DYET and LGMB, its alphabet position (A = 1 ... Z = 26).

2. Compare the two clusters position by position to find the fixed shift between them (see the table below).

Every letter moves forward by exactly 8 alphabet positions, wrapping past Z where needed, so +8 is the fixed shift that produces LGMB from DYET.

1. Apply this same +8 shift to LGMB, the last given cluster, to build the missing cluster.

2. L (12) + 8 = 20 -> T

3. G (7) + 8 = 15 -> O

4. M (13) + 8 = 21 -> U

5. B (2) + 8 = 10 -> J

Reading these letters in order gives the missing cluster: TOUJ.

Applying this same +8, letter-by-letter check to every offered cluster shows the shift holds for all four letters in only one of them. In the others, at most the first one or two letters follow +8 while the remaining letters follow a different, inconsistent shift, confirming TOUJ as the only cluster consistent with the rule established between DYET and LGMB.