Which of the following terms will replace the question mark (?) in the given series? ABNI, DAQH, ?, JYWF

Correct — C.

Treat the four letter positions as four separate series.

Rule: 1st +3, 2nd −1, 3rd +3, 4th −1.

1st: A, D, G, J
2nd: B, A, Z, Y — one step back from A wraps to Z
3rd: N, Q, T, W
4th: I, H, G, F

The missing term is GZTG → option (c).

Why the others are wrong

• (a)
  CAYG — CAYG opens with C, but the first letters run A, D, ?, J in steps of +3, which fixes G. C would need a jump of +2 and then +7.
• (b)
  TGZG — TGZG carries plausible letters in the wrong slots. The first position belongs to the +3 series A, D, G, J, so T cannot lead.
• (d)
  GTZG — GTZG gets the outer letters right and swaps the middle pair. The second position follows B, A, Z, Y, so Z belongs second and T third.

A four-letter cluster series is four independent single-letter series stacked together. Write the alphabet positions down before hunting for a pattern.

With A = 1 and Z = 26, the four columns here read 1, 4, 7, 10 and 2, 1, 26, 25 and 14, 17, 20, 23 and 9, 8, 7, 6.

Two columns climb by 3 and two fall by 1, and the fall in the second column wraps past A into Z, which is what puts Z into the answer.

Key facts

• The 1st and 3rd letters both advance by 3: A, D, G, J and N, Q, T, W.
• The 2nd and 4th letters both fall by 1: B, A, Z, Y and I, H, G, F.
• One step back from A is Z, so the alphabet is treated as a loop.

Common traps

• Stopping the second column at A instead of wrapping it round to Z
• Matching on the first letter alone — options (c) and (d) both begin with G and differ only in the middle two letters

No directly related past PYQ was found.