In this letter-based odd-man-out question, four groups of three letters are given: EHK, ZBD, LOR and SVY. In three of these groups, each successive letter is exactly three positions ahead of the previous letter in the English alphabet. Which letter group is the odd one out because it does not follow this constant +3 pattern?

Introduction / Context:
This is an alphabet series odd-man-out question from logical reasoning. The options are groups of three letters, and you must detect a consistent positional pattern followed by most groups. Alphabet questions test your ability to map letters to their positions (A=1, B=2, C=3 and so on) and observe differences between consecutive letters. Here, three of the groups follow a neat pattern where each letter is three steps ahead of the previous one. The fourth group breaks this pattern and must be identified as the odd one out.

Given Data / Assumptions:
Letter groups: EHK, ZBD, LOR and SVY.
We consider the English alphabet positions A=1 to Z=26.
In three groups, the difference between adjacent letters is constant and equal to +3 positions.
The remaining group does not follow this constant-difference rule and is the required odd option.

Concept / Approach:
The basic approach is to convert each letter into its numeric position in the alphabet and check the step size between consecutive letters. If, for example, E(5) to H(8) is a difference of +3, and H(8) to K(11) is again +3, then this group maintains a constant progression. For an odd-man-out question, you look for the one group where the step pattern changes or becomes inconsistent. In this case, we will pay special attention to whether the group respects a +3, +3 movement throughout.

Step-by-Step Solution:
Step 1: For EHK, positions are E=5, H=8 and K=11. Differences are 8 - 5 = 3 and 11 - 8 = 3. This group follows +3 and +3. Step 2: For LOR, positions are L=12, O=15 and R=18. Differences are 15 - 12 = 3 and 18 - 15 = 3, so this group also follows +3 and +3. Step 3: For SVY, positions are S=19, V=22 and Y=25. Differences are 22 - 19 = 3 and 25 - 22 = 3, again matching the +3 and +3 pattern. Step 4: For ZBD, positions are Z=26, B=2 and D=4. If we move forward cyclically after Z, then from Z (26) to B (2) is effectively +2 positions (Z to A to B is two steps) or a nonstandard jump, and from B (2) to D (4) is +2. This pair of differences does not match +3 and +3 in a simple linear way. Step 5: Conclude that ZBD does not follow the same +3, +3 pattern as the other three groups, so it is the odd one out.
Verification / Alternative check:
You can also verify visually by writing the alphabet in a row and counting the spaces between letters. E to H and H to K each skip two letters in between, as do L to O and O to R, and S to V and V to Y. That is, each move jumps over exactly two letters. Trying the same idea for ZBD gives an inconsistent jump that does not match the others, confirming that this group is structurally different from the rest.

Why Other Options Are Wrong:
EHK obeys the rule where each subsequent letter is three alphabet positions ahead of the previous one, so it fits the main pattern.
LOR also shows a consistent +3 step between letters and therefore belongs to the majority group.
SVY exactly matches the same +3 difference between adjacent letters and is clearly not the odd group.
ZBD alone fails to exhibit this clean +3, +3 pattern, making it the only valid odd-man-out choice.

Common Pitfalls:
A frequent mistake is to focus on the shapes or sounds of letters instead of the alphabet positions. Some students may also miscount the cyclical movement around Z and treat it as if it naturally continues, which can be confusing. In exam conditions, always stick to a clear numeric method and compute exact differences. Another pitfall is to assume that any irregular group is correct without checking all groups systematically, which may lead to errors when two or more groups look unusual at first glance.

Final Answer:
The only letter group that does not follow the constant +3, +3 alphabet pattern is ZBD.