In the alphabet pair series RQ, ST, VU, WX, which of the following pairs should come next to follow the same pattern?

Introduction / Context:
This question gives a series of letter pairs: RQ, ST, VU, WX, ?. The pattern is hidden in how the first letters and second letters move through the alphabet. The candidate must analyse both positions to uncover a regular rule, often involving alternating step sizes or mirrored movements, and then apply this rule to generate the next pair in the sequence.

Given Data / Assumptions:

• Given pairs: RQ, ST, VU, WX, ?.• First letters form the sub-series: R, S, V, W.• Second letters form the sub-series: Q, T, U, X.• Alphabet positions A=1, B=2, ..., Z=26 will be used.

Concept / Approach:
We treat each pair as a point with coordinates (first letter position, second letter position). By examining the numeric differences between consecutive pairs, we try to detect a repeating pattern of increments. Frequently, the increments themselves alternate between two values, such as +1 and +3. Once this alternating pattern is established for both first and second letters, the next pair can be determined by applying the appropriate increment to the last known pair.

Step-by-Step Solution:
First letters: R=18, S=19, V=22, W=23.Differences: S−R = +1, V−S = +3, W−V = +1.Thus the pattern for first letters is +1, +3, +1, so the next step should be +3.Next first letter = 23 + 3 = 26, which is Z.Second letters: Q=17, T=20, U=21, X=24.Differences: T−Q = +3, U−T = +1, X−U = +3.So the pattern for second letters is +3, +1, +3, implying that the next step should be +1.Next second letter = 24 + 1 = 25, which is Y.Hence, the next pair in the series is ZY.

Verification / Alternative check:
We can summarise the first letters as 18, 19, 22, 23, 26 and the second letters as 17, 20, 21, 24, 25. The sequence of increments for the first coordinates is +1, +3, +1, +3 and for the second coordinates is +3, +1, +3, +1. These alternating patterns are symmetric and consistent. ZY fits perfectly as the next pair while preserving the established structure, which confirms it as the logically correct choice.

Why Other Options Are Wrong:
OP and PO jump backwards relative to WX and therefore violate the forward-moving pattern. YZ reverses the order of letters that the increment rules predict, since the first coordinate must be 26 and the second 25, not the other way round. Consequently, these pairs break the carefully alternating increment structure and cannot be accepted as correct continuations of the series.

Common Pitfalls:
Some learners may try to match only the rough positions in the alphabet or notice that the pairs seem vaguely mirrored without doing the exact calculations. Others may incorrectly assume a constant difference. The reliable approach is always to convert letters into their numeric positions and carefully compute the sequence of differences between successive terms.

Final Answer:
ZY