In the following question, four letter groups are given: DEB, RTP, HIF and NOL. Three of these follow a similar alphabetical pattern, and one is different. Which letter group is different from the other three responses?

Introduction / Context:
This is a letter classification question involving patterns based on alphabetical positions. You are given four three-letter combinations: DEB, RTP, HIF and NOL. Three follow the same positional pattern in the alphabet, but one breaks the rule. Such questions test your ability to convert letters into numerical positions (A = 1, B = 2, ..., Z = 26) and observe consistent differences between the letters in each group.

Given Data / Assumptions:
• The letter groups given are: DEB, RTP, HIF and NOL.• We use standard English alphabetical positions.• We are looking for a consistent pattern in three groups and one group that does not obey that pattern.

Concept / Approach:
A systematic approach is to translate each letter into its alphabetical position and then examine the differences between the first, second and third letters. For three of the groups, the pattern is that the second letter is one position after the first, and the third letter is three positions before the second. In notation, second = first + 1 and third = second − 3. The group that does not follow this pattern will be the odd one out.

Step-by-Step Solution:
Step 1: Convert DEB into positions: D = 4, E = 5, B = 2.Step 2: Check the differences: from D to E is +1 (4 to 5), from E to B is −3 (5 to 2). So DEB follows the +1, −3 pattern.Step 3: Convert HIF: H = 8, I = 9, F = 6.Step 4: Differences: from H to I is +1 (8 to 9), from I to F is −3 (9 to 6). So HIF also follows +1, −3.Step 5: Convert NOL: N = 14, O = 15, L = 12.Step 6: Differences: from N to O is +1 (14 to 15), from O to L is −3 (15 to 12). So NOL again follows +1, −3.Step 7: Convert RTP: R = 18, T = 20, P = 16.Step 8: Differences: from R to T is +2 (18 to 20), from T to P is −4 (20 to 16). This is not +1, −3 like the others.Step 9: Therefore, RTP does not follow the same pattern and is the odd one out.

Verification / Alternative check:
Re-check the pattern across the three consistent groups: DEB, HIF and NOL. In each, letters are close in the alphabet with a gentle rise then a small drop. RTP, however, jumps further, skipping one additional letter in both steps. If we tried to impose a different pattern, it would group only two items at a time; the only pattern that neatly groups three items is the +1, −3 rule, leaving RTP as the unique exception.

Why Other Options Are Wrong:
DEB: Fits the pattern with +1 then −3 differences.HIF: Also fits the same sequence of differences.NOL: Again follows +1 then −3, matching DEB and HIF.None of these: Incorrect because we have clearly found one group, RTP, that does not match the others.

Common Pitfalls:
A common error is to look only at visual similarity or at the first letters and ignore the precise numeric differences. Another mistake is to stop after testing just one or two groups and miss the consistent pattern among three of them. Always check each group carefully and write out the position numbers to reveal hidden arithmetic patterns. Here, this simple discipline reveals that RTP is the only group with +2 and −4 rather than +1 and −3, so it must be the odd one out.

Final Answer:
The letter group that is different from the other three is RTP.