Four letter-clusters have been given, out of which three are alike in some manner and one is different. Select the one 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 — C. Rule: inside each cluster the gaps run -2 then -3.

Y W T is 25, 23, 20, giving -2 then -3.
X V S is 24, 22, 19, giving -2 then -3.
Z X U is 26, 24, 21, giving -2 then -3.

W U Q is 23, 21, 17, giving -2 then -4. The second gap is one letter too wide, so this is the different cluster, option (c).

Why the others are wrong

• (a)
  YWT — Y W T runs 25, 23, 20 — a drop of 2 and then a drop of 3, which is the shared pattern.
• (b)
  XVS — X V S runs 24, 22, 19 — the same -2, -3 gaps, simply started one letter lower.
• (d)
  ZXU — Z X U runs 26, 24, 21 — again -2, -3, this time started from the end of the alphabet.

Write the three position numbers under each cluster, then write the two gaps under those. The whole question lives in that second row of numbers.

Here three clusters give -2, -3 and one gives -2, -4. Which letters they start from is irrelevant.

The note is doing real work: it tells you not to spend time on vowels, consonants or where they sit, so go straight to the arithmetic.

Key facts

• Y is 25, W is 23 and T is 20, so YWT has gaps of -2 and -3.
• WUQ is 23, 21, 17, so its second gap is -4.
• XVS and ZXU both repeat the -2, -3 pattern.

Common traps

• Comparing starting letters instead of the gaps between letters.
• Miscounting W as 22 when it is the 23rd letter.
• Stopping after the first gap, which is -2 in all four clusters.

No directly related past PYQ was found.