Based on the English alphabetical order, three of the following four letter-clusters are alike in a certain way and thus form a group. Which is the one that DOES NOT belong to that group? (Note: The odd man out is not based on the number of consonants/vowels or their position in the letter-cluster.)

Correct — D. Rule: each cluster is three consecutive letters written backwards, one step down the alphabet at every move.

H G F is 8, 7, 6.
V U T is 22, 21, 20.
K J I is 11, 10, 9.

A A Y is 1, 1, 25. The first move does not step down at all, because A repeats, so this cluster breaks the rule and is option (d).

Even reading the alphabet as a cycle, where the letter below A is Z, the printed middle letter is A and not Z, so the cluster still fails.

Why the others are wrong

• (a)
  HGF — H G F steps 8 to 7 to 6, one letter down at each move, which is the rule the group shares.
• (b)
  VUT — V U T steps 22 to 21 to 20 — the same one-letter descent, started higher up the alphabet.
• (c)
  KJI — K J I steps 11 to 10 to 9, again consecutive and descending, so it belongs with the other two.

Odd-one-out on letter clusters is a question about differences. Convert each cluster to numbers first, then write the gaps underneath.

H G F becomes 8, 7, 6 with gaps of -1 and -1. Do that for all four clusters and the outlier is usually visible without further thought.

The note under the question closes off the shortcuts. You may not answer on vowel counts or vowel positions, which is SSC telling you the answer is in the numbers.

Key facts

• HGF, VUT and KJI are each three consecutive letters in reverse order.
• AAY repeats its first letter, so its first gap is 0 rather than -1.
• The note rules out any answer based on vowel counts or vowel positions.

Common traps

• Hunting for a vowel pattern, which the note explicitly excludes.
• Reading AAY as AZY and concluding that all four clusters fit.
• Converting some clusters to numbers and eyeballing the rest.

No directly related past PYQ was found.