In this alphabet series odd-man-out question, four groups of letters are given: BDGK, JLOS, NPSW and MORU. In three of these groups, the positional differences between consecutive letters follow the pattern +2, +3 and +4. Which letter group is the odd one out because it does not maintain this +2, +3, +4 pattern?

Introduction / Context:
This problem is an alphabet series odd-man-out question. The four letter groups given are BDGK, JLOS, NPSW and MORU. Alphabet series questions frequently rely on the numeric positions of letters (A=1, B=2 and so on) and the differences between consecutive letters in each group. Here, three groups obey a regular pattern of increasing steps of +2, +3 and +4, whereas one group breaks this rule. The task is to identify which group does not maintain the same sequence of differences.

Given Data / Assumptions:
The letter groups are BDGK, JLOS, NPSW and MORU.
Positions in the alphabet are A=1, B=2, C=3, ..., Z=26.
In three groups, the difference between first and second letter is +2, between second and third is +3, and between third and fourth is +4.
One group does not follow the +2, +3, +4 pattern and is the odd one out.

Concept / Approach:
The approach is to convert each letter to its alphabet position and compute differences between consecutive letters. In patterns like +2, +3, +4, each step increases by 1 more than the previous step. By checking each group in detail, we can identify whether the pattern is maintained. The odd group breaks the step pattern in at least one place, which makes it different from the others.

Step-by-Step Solution:
Step 1: For BDGK, positions are B=2, D=4, G=7 and K=11. Step 2: Compute differences for BDGK: D - B = 4 - 2 = 2, G - D = 7 - 4 = 3, K - G = 11 - 7 = 4. Pattern is +2, +3, +4. Step 3: For JLOS, positions are J=10, L=12, O=15 and S=19. Step 4: Compute differences for JLOS: L - J = 12 - 10 = 2, O - L = 15 - 12 = 3, S - O = 19 - 15 = 4. Pattern is again +2, +3, +4. Step 5: For NPSW, positions are N=14, P=16, S=19 and W=23. Step 6: Compute differences for NPSW: P - N = 16 - 14 = 2, S - P = 19 - 16 = 3, W - S = 23 - 19 = 4. Pattern is +2, +3, +4. Step 7: For MORU, positions are M=13, O=15, R=18 and U=21. Step 8: Compute differences for MORU: O - M = 15 - 13 = 2, R - O = 18 - 15 = 3, U - R = 21 - 18 = 3. Here the pattern is +2, +3, +3, not +2, +3, +4. Step 9: Conclude that MORU is the only group that does not have the +2, +3, +4 progression, so it is the odd one out.
Verification / Alternative check:
A quick visual check can also be done by writing the letters of each group on an alphabet line and counting the letters skipped. In BDGK, you skip 1 letter (C) then 2 letters (E, F) then 3 letters (H, I, J). Similarly, JLOS and NPSW show the same increasing skip pattern. In MORU, however, the last jump from R to U does not skip 3 letters but only 2 (S and T), which confirms that it is different. This alternative representation validates the numeric difference method.

Why Other Options Are Wrong:
BDGK consistently follows the +2, +3, +4 pattern and therefore belongs to the main group of correctly structured letter sequences.
JLOS also shows the same increasing step pattern and is not the odd one out.
NPSW again follows the identical +2, +3, +4 pattern and must be grouped with BDGK and JLOS.
MORU alone breaks the pattern with the final step being only +3 instead of +4, making it the logically odd sequence.

Common Pitfalls:
Some candidates may focus only on the first difference and ignore the rest, which can lead to incorrect conclusions. Another frequent mistake is miscounting positions due to forgetting the numeric values of some letters. It is helpful to mentally recall anchor letters like A=1, M=13 and Z=26 to keep track of positions. Also, avoid overcomplicating the pattern; once a simple and consistent explanation fits three options, the remaining one that does not fit is usually the correct odd-man-out answer.

Final Answer:
The letter group that does not follow the +2, +3, +4 step pattern is MORU.