In this alphabet series reasoning question, select the odd group of letters from the given alternatives based on the backward step pattern between letters.

Introduction / Context:
This non verbal reasoning question is based on patterns in groups of three letters. Each option contains three letters in a specific order. Your task is to identify which group does not follow the same alphabetic step pattern as the others. Such questions train candidates to work comfortably with forward and backward sequences in the English alphabet.

Given Data / Assumptions:
- The letter groups are HFD, SQO, ZXV, and BZU.- All letters belong to the English alphabet.- We will examine how the letters move from left to right in each group.

Concept / Approach:
A structured approach is to convert each letter into its alphabet position and then compute the difference between consecutive letters. If three groups show a constant pattern, such as a fixed step of minus 2 when moving backward through the alphabet, and one group does not, that non matching group is the odd one out. We apply this technique to all four groups.

Step-by-Step Solution:
Step 1: For HFD, positions are H = 8, F = 6, D = 4. Differences are minus 2 and minus 2, so the sequence moves backward by 2 each time.Step 2: For SQO, positions are S = 19, Q = 17, O = 15. Differences are minus 2 and minus 2 again, so it matches the same backward step pattern.Step 3: For ZXV, positions are Z = 26, X = 24, V = 22. Differences are minus 2 and minus 2, also fitting the pattern.Step 4: For BZU, positions are B = 2, Z = 26, U = 21. Differences are plus 24 and minus 5, which do not follow a constant backward step of minus 2.Step 5: Therefore, three groups show a uniform backward movement of minus 2, while BZU has irregular jumps.

Verification / Alternative check:
You can also observe that HFD, SQO, and ZXV can each be read as a simple backward run skipping one letter between each term. In contrast, BZU jumps from B to Z across almost the entire alphabet and then drops suddenly to U, which clearly breaks the pattern.

Why Other Options Are Wrong:
HFD: Regular backward sequence with step minus 2.SQO: Also a backward sequence with the same step.ZXV: Again follows the minus 2 backward pattern.

Common Pitfalls:
Some candidates check only whether the letters are moving backward and ignore the size of the jump. The size of the step is crucial here, because all three correct groups share both the direction and the step size.

Final Answer:
The odd letter group is BZU because it does not follow the constant backward minus 2 step pattern that the other groups follow.