In the following alphabet reasoning question, four three letter groups are given (DEB, RTP, HIF and NOL). In three of these groups, the first two letters are consecutive in the alphabet, while in one group they are not. Find the odd word or letter group from the given alternatives.

Introduction / Context:
This question is about recognising simple letter patterns in the English alphabet. You are given four groups of three letters: DEB, RTP, HIF and NOL. The pattern is hidden in the relation between the first and second letters of each group. Most groups have the first two letters consecutive in the alphabet, while one group breaks this consecutive pattern. You must identify that group as the odd one out.

Given Data / Assumptions:

• Letter groups: DEB, RTP, HIF and NOL.
• Alphabet positions: A = 1, B = 2, ..., Z = 26.
• We focus mainly on the relationship between the first and second letters.
• In three groups, the first two letters are consecutive alphabetically.
• Exactly one group does not have consecutive first and second letters.

Concept / Approach:
The approach is to examine each group and check whether the second letter is exactly one step after the first letter in the alphabet. If so, the pair is consecutive. If the difference is greater than 1, the pair is not consecutive. Once you have checked all four groups, the one where the first two letters do not form a consecutive pair will stand out as the odd group. This type of pattern is very common in coding and series questions involving letters.

Step-by-Step Solution:
Step 1: Analyse DEB.D = 4 and E = 5. Since 5 - 4 = 1, D and E are consecutive letters. The third letter B is not relevant to this particular pattern.Step 2: Analyse HIF.H = 8 and I = 9. Here 9 - 8 = 1, so H and I are consecutive letters. Third letter F is separate.Step 3: Analyse NOL.N = 14 and O = 15. Again 15 - 14 = 1, so N and O are consecutive letters.Step 4: Analyse RTP.R = 18 and T = 20. Now 20 - 18 = 2, which means R and T are not consecutive; there is one letter S between them.Step 5: Identify the odd group.Three groups (DEB, HIF and NOL) have first two letters consecutive, while RTP does not. Thus RTP is the odd one out.

Verification / Alternative check:
A quick visual check is to write the alphabet and mark the first two letters of each group. You will see D E, H I and N O appear as neighbours, but R and T appear with S between them. This clearly shows that RTP breaks the consecutive pattern. When you notice such patterns, always compare all options to be sure there is exactly one exception.

Why Other Options Are Wrong:
DEB: D and E are consecutive letters, so this group follows the main rule.
HIF: H and I are consecutive, so this group also fits the pattern.
NOL: N and O are consecutive, so this group belongs with DEB and HIF.

Common Pitfalls:
Sometimes students get distracted by the third letter and try to force a more complicated rule involving all three positions. In many exam questions, however, the key difference rests only in part of the group, such as the first two letters. Therefore, always check simple relationships first, such as adjacency or fixed gaps in the alphabet, before looking for more complex structures.

Final Answer:
The odd letter group is RTP, because its first two letters are not consecutive in the alphabet, while the first two letters of the other groups are consecutive pairs.