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...11

Correct — C.

Rule: the three letters of each cluster sit at equal gaps of +2 and +2.

TVX: T(20) → V(22) → X(24), gaps +2, +2.
HJL: H(8) → J(10) → L(12), gaps +2, +2.
NPR: N(14) → P(16) → R(18), gaps +2, +2.

MOP: M(13) → O(15) → P(16), gaps +2, +1.

The second gap is one, not two, so option (c) is the cluster that does not belong.

Why the others are wrong

• (a)
  TVX — TVX runs T(20), V(22), X(24) on gaps of +2 and +2. It sits with the group, so it cannot be the odd one out.
• (b)
  HJL — HJL runs H(8), J(10), L(12), the same +2, +2 spacing lower down the alphabet. It belongs to the group.
• (d)
  NPR — NPR runs N(14), P(16), R(18), again +2, +2. Position in the alphabet is irrelevant, only the gaps are.

Odd-one-out on letter clusters is a question about gaps, not about the letters themselves. Convert each cluster to alphabet positions and read the differences.

Three clusters here share the difference pattern +2, +2 and one does not. Nothing else about the clusters carries information.

The printed note rules out counting vowels and consonants or their placement. That matters here, because MOP is also the cluster carrying a vowel, and the note closes off that competing route to the same answer.

Key facts

• TVX, HJL and NPR all run on a gap of +2 followed by another +2.
• MOP runs +2 then +1, because O is the 15th letter and P the 16th.
• The printed note bars vowel and consonant counting as the basis of the answer.

Common traps

• Choosing MOP because it is the cluster containing a vowel, a route the printed note rules out.
• Counting letters skipped rather than differences in position, which shifts every gap by one.

No directly related past PYQ was found.