Select the letter-cluster from among the given options that can replace the question mark (?) in the following series. GEA, IJH, KOO, MTV ?

Correct — A.
Rule: each position keeps its own step: +2, +5, +7.

1st letters: G, I, K, M → O (+2 each time)
2nd letters: E, J, O, T → Y (+5)
3rd letters: A, H, O, V → V + 7 = 22 + 7 = 29, and 29 − 26 = 3 = C

The next cluster is OYC → option (a).

Why the others are wrong

• (b)
  OYD — OYD puts D in the 3rd place, which is V + 8. The 3rd letters step +7 (A, H, O, V), and V + 7 wraps to C.
• (c)
  OYB — OYB puts B in the 3rd place, which is V + 6, one step short. Counting seven on from V, W X Y Z A B C, lands on C.
• (d)
  PZD — PZD misses all three steps: M + 2 is O, not P, T + 5 is Y, not Z, and V + 7 is C, not D.

This series is three separate series stacked together. Read the 1st letters down the list, then the 2nd, then the 3rd, and find each step on its own.

Turn letters into positions (A = 1 … Z = 26) to see the steps. When a sum passes 26, subtract 26 to wrap back to the start of the alphabet.

Key facts

• 1st letters step +2: G, I, K, M, O.
• 2nd letters step +5: E, J, O, T, Y.
• 3rd letters step +7: A, H, O, V, C.

Common traps

• Stopping at Z when a step runs past it, instead of carrying on from A
• Finding the step in one position and assuming the others share it

No directly related past PYQ was found.