Four letter-clusters have been given, out of which three are alike in some manner and one is different. Select the letter-cluster that is different. Note: The odd one out is not based on the number of consonants/vowels or their position in the letter cluster.

Correct — B. Convert each cluster to alphabet positions and read the two gaps inside it.

Rule: first +4 gives the second, second −2 gives the third.

L(12) P(16) N(14): +4 then −2 ✓
H(8) L(12) J(10): +4 then −2 ✓
B(2) F(6) D(4): +4 then −2 ✓
G(7) I(9) K(11): +2 then +2 ✗

GIK is the cluster that breaks the pattern → option (b).

Why the others are wrong

• (a)
  LPN — LPN runs L → P as +4 and P → N as −2, exactly the gaps HLJ and BFD use. Its letters being late in the alphabet is not what the question separates on.
• (c)
  HLJ — HLJ runs +4 then −2 as well. It also dips at the third letter, which is the visible signature of the group of three.
• (d)
  BFD — BFD repeats the +4, −2 shape at the very start of the alphabet. Where a cluster sits in the alphabet is not a difference in kind.

Letter-cluster odd-one-out items are arithmetic in disguise. Write A = 1 through Z = 26, convert, and compare the gaps between consecutive letters rather than the letters themselves.

Three of these clusters rise by 4 and then fall back by 2, which is why each one ends on a letter lower than its middle letter. GIK rises twice and never falls.

A second reading picks the same cluster: LPN, HLJ and BFD sit entirely on even positions and GIK entirely on odd ones. When two independent readings agree, you can commit quickly.

Key facts

• A = 1 through Z = 26 is the position map every letter-cluster item uses.
• LPN, HLJ and BFD all run +4 then −2, while GIK runs +2 then +2.
• LPN, HLJ and BFD use only even alphabet positions and GIK uses only odd ones.

Common traps

• Counting vowels and consonants, which the stem's NOTE rules out before you begin.
• Sorting the letters first. LPN sorted becomes LNP and the +4, −2 signature disappears.
• Checking the first gap and stopping. Here it happens to settle the question, but on a four-letter cluster it usually does not.

No directly related past PYQ was found.