​Out of the four letter-clusters listed, three are alike in some manner and one is different. Select the odd one.​

Correct option is B

 Check relationships between letters

• Option A (NK): N (14th letter) → K (11th letter)
  Difference: $14-11=3$

• Option B (QA): Q (17th letter) → A (1st letter)
  Difference: $17-1=16$

• Option C (XU): X (24th letter) → U (21st letter)
  Difference: $24-21=3$

• Option D (GD): G (7th letter) → D (4th letter)
  Difference: $7-4=3$

  $All\; have\; the\; same\; difference\; 3\; but\; QA\; has\; difference\; 16\; which\; is\; odd\; from\; the\; others.$