In this alphabet pattern reasoning question, select the odd group of letters from the following alternatives: BGF, FDH, BAE and CDE.

Introduction / Context:
This question belongs to the letter arrangement and pattern recognition section of aptitude tests. You are given four groups of letters BGF, FDH, BAE and CDE and asked to choose the odd group. Three of the groups are jumbled sequences that do not show a simple increasing consecutive order, while one group forms a neat run of consecutive letters in proper alphabetical sequence. Your goal is to detect this structural difference.

Given Data / Assumptions:

• Letter groups: BGF, FDH, BAE and CDE.
• We use alphabetical positions: A = 1, B = 2, ..., Z = 26.
• Exactly one group should stand out based on a clear and simple pattern.
• We assume that consecutive letter order and regular spacing are the key ideas.

Concept / Approach:
An efficient way to handle such questions is to check whether the letters in each group are consecutive in the alphabet and whether they appear in forward order. If only one group is made of three consecutive letters in correct order, and the others are either mixed or have irregular gaps, then that one group is the odd one. We will examine each triplet and compare its internal structure with the others.

Step-by-Step Solution:
Step 1: Analyze CDE.C, D and E occupy positions 3, 4 and 5. They are three consecutive letters in perfect forward alphabetical order.Step 2: Analyze BGF.B, G and F have positions 2, 7 and 6. These letters are not consecutive and the order 2, 7, 6 is neither a simple forward sequence nor a reverse sequence of consecutive letters.Step 3: Analyze FDH.F, D and H have positions 6, 4 and 8. Again they are not in straightforward consecutive order, and there is no simple consistent step between them.Step 4: Analyze BAE.B, A and E have positions 2, 1 and 5. Here A and B are consecutive but the order is 2 to 1 to 5, which is still not a pure forward sequence of three consecutive letters.Step 5: Compare all four groups.CDE is the only group that shows three letters that are consecutive and correctly ordered in the alphabet, while the other groups are jumbled or irregular.

Verification / Alternative check:
Write down the alphabet and quickly mark each group. You will see that C, D and E sit next to each other in a straight line. For BGF, FDH and BAE you must jump back and forth along the alphabet to move from one letter to the next, and there is no equal-gap pattern that uniquely holds in all three. This visual check confirms that CDE has a neat structure that is absent in the others, which makes it the odd group based on a clean and testable rule.

Why Other Options Are Wrong:
BGF: Letters are not consecutive and appear in a mixed order, so they do not share the simple pattern seen in CDE.
FDH: Also a mixed group with irregular spacing between letters rather than a straightforward sequence.
BAE: Contains a partial adjacency (A and B) but still does not form three consecutive letters in proper order.

Common Pitfalls:
Some learners may look for complex arithmetic differences between letter positions and miss the most basic pattern of consecutive letters. In many reasoning exams, the intended rule is very simple, such as consecutive runs like ABC or CDE. Always check for these straightforward patterns before assuming a more complicated rule. This habit saves time and improves accuracy when dealing with letter series questions.

Final Answer:
The odd group of letters is CDE, because it is the only group that consists of three consecutive letters in correct alphabetical order, while the other groups are jumbled or irregular sequences.