Select the letter-cluster from among the given options that can replace the question mark (?) in the following series: M C K J H N G M Q D R T ?

Correct — C.
Rule: first letter −3, second letter +5, third letter +3.

First: M(13), J(10), G(7), D(4) → A(1).
Second: C(3), H(8), M(13), R(18) → W(23).
Third: K(11), N(14), Q(17), T(20) → W(23).

That gives AWW → option (c).

Why the others are wrong

• (a)
  AES — AES gets the first letter right, then breaks. R + 5 is W, not E, and T + 3 is W, not S.
• (b)
  IJS — IJS fails at the first letter: D − 3 is A(1), not I(9). J and S are off the +5 and +3 steps as well.
• (d)
  RDS — RDS starts with R, but the first letters fall by 3 (M, J, G, D), so the next is A. D and S miss the W that both other positions need.

A letter-cluster series is three letter series running side by side. Number the alphabet (A = 1 … Z = 26) and read one position at a time down the clusters.

Here each position has its own step: the first letters fall by 3, the second rise by 5, the third rise by 3. Reading across a cluster (M, C, K) shows no steady step, which is the signal to read down instead.

Key facts

• The first letters step −3: M, J, G, D, A.
• The second letters step +5: C, H, M, R, W.
• The third letters step +3: K, N, Q, T, W.

Common traps

• Reading each cluster left to right as a word instead of reading each position down the series
• Rejecting AWW because a letter repeats, though each W comes from its own step
• Using one step for every position after checking only the first letters

No directly related past PYQ was found.