In the following group of three letter clusters BHF, LDJ, OKG and ZTY, three of the clusters are alike in a certain specific way and thus form a group. Which one of these clusters does not belong to that group based on the underlying alphabetical pattern?

Introduction / Context:
This is an odd one out question based on letter patterns. We are given the three letter clusters BHF, LDJ, OKG and ZTY and asked to find which cluster does not follow the same rule as the others. Such problems appear frequently in alphabet test sections and are designed to check your ability to detect regularities and numerical relationships between letter positions in the English alphabet.

Given Data / Assumptions:

The clusters are BHF, LDJ, OKG and ZTY, each made of three letters.
Alphabet positions are B 2, H 8, F 6; L 12, D 4, J 10; O 15, K 11, G 7; Z 26, T 20, Y 25.
We need to compare the differences between consecutive letters inside each cluster.
The odd cluster will be the one whose internal pattern differs from the common pattern seen in the other three clusters.

Concept / Approach:
The usual approach is to convert each letter into its position number in the alphabet and then study how far apart the letters are. We can compute the absolute difference between the first and second letters, and between the second and third letters for every cluster. If three of them share a similar structure in their differences and one does not, the different one will be identified as the odd one out. This numeric method removes guesswork and makes the comparison very clear.

Step-by-Step Solution:

Verification / Alternative check:
To verify, you can check the pattern in another way. For BHF, LDJ and ZTY, the distance between the first and second letter is always different from the distance between the second and third letter. However, OKG is the only case where the pattern shows equal spacing between consecutive letters. Since we are looking for a group of three that share a common characteristic, the unique equal gap property of OKG clearly separates it from the others and confirms that it is the odd one out.

Why Other Options Are Wrong:

BHF has differences 6 and 2, which follow the unequal gap pattern similar to the other non odd clusters and so it belongs to the main group.
LDJ has differences 8 and 6, again showing unequal spacing and therefore fits the dominant pattern rather than being an exception.
ZTY has differences 6 and 5, which are also unequal and consistent with the structure of the majority of clusters, so it cannot be treated as the odd one out.

Common Pitfalls:
A common mistake in such questions is to focus on superficial features like the presence of vowels or whether letters are near the beginning or end of the alphabet. Another error is to look only at a single difference, such as the gap between the first and second letter, and ignore the rest. Always examine both internal gaps for each cluster to avoid missing the actual structural pattern that the question is designed to test.

Final Answer:
The letter cluster that does not belong to the group and is therefore the odd one out is OKG.