Select the letter-cluster from among the given options that can replace the question mark (?) in the following series. GHZ, HIY, IJX, JKW, ?

Correct — B.
Rule: three columns: +1, +1 and −1.

First letters: G, H, I, J → K.
Second letters: H, I, J, K → L.
Third letters: Z, Y, X, W → V, counting back from Z.

The next cluster is KLV → option (b).

Why the others are wrong

• (a)
  JHG — JHG starts with J, which the fourth term already used. The first letters climb G, H, I, J, so the fifth must start with K.
• (c)
  KMN — KMN has the right K but then jumps to M, where the second column needs L. Its N also breaks the third column, which falls Z, Y, X, W to V.
• (d)
  HGK — HGK moves the first column back to H, but G, H, I, J climbs to K. Its G and K also miss the L and V the other two columns need.

A letter-cluster series is three letter series read column by column. Write down the first letters of every term, then the second letters, then the third, and find the step in each column.

Here two columns climb one letter at a time, while the third walks backwards from Z: Z, Y, X, W. The columns are independent, so the answer takes one letter from each: K, L, V.

Key facts

• G = 7, H = 8, I = 9, J = 10, K = 11: the first letters climb by 1.
• Z = 26, Y = 25, X = 24, W = 23, V = 22: the third letters fall by 1.
• In a cluster series, each position inside the cluster is its own series.

Common traps

• Matching only the first letter and picking KMN
• Assuming all three columns move forward when the third runs backwards

No directly related past PYQ was found.