Select the option that is related to the fifth letter-cluster in the same way…

Concept: every letter carries a fixed alphabet position (A = 1, B = 2, and so on up to Z = 26), and a letter-cluster analogy is fixed by two independent choices — which letter of the source cluster is paired with which letter of the target cluster, and what constant step is added to each pair. The pairing need not run letter-for-letter in the given order; it may run in reverse. A rule counts as established only when one pairing together with one set of steps reproduces every example the question supplies.

Application: test both candidate pairings against the two examples that are given.

1. Same-order pairing on G P K to M S I: G(7) to M(13) is a step of +6, P(16) to S(19) is +3, and K(11) to I(9) is -2.

2. Same-order pairing on R H T to V K T: R(18) to V(22) is +4, H(8) to K(11) is +3, and T(20) to T(20) is 0. The outer steps do not agree with the previous example, so no single same-order rule covers both.

3. Reversed pairing on G P K to M S I, reading the source backwards as K, P, G: K(11) to M(13) is +2, P(16) to S(19) is +3, and G(7) to I(9) is +2.

4. Reversed pairing on R H T to V K T, reading the source backwards as T, H, R: T(20) to V(22) is +2, H(8) to K(11) is +3, and R(18) to T(20) is +2. Both examples obey the same three steps, so the rule is: reverse the cluster, then add 2, 3 and 2 to its successive letters.

Applying that rule to I D W, which read backwards is W, D, I:

Cross-check: the same rule regenerates both supplied pairs exactly, turning G P K into M S I and R H T into V K T. Omitting the reversal step would instead produce K G Y, the same three letters in source order. With the reversal applied, I D W maps to Y G K.