A two letter series is given as DP, EY, FJ, ? Choose the correct alternative from the options that will complete this series based on positions in the English alphabet.

Introduction / Context:
This alphabet test question presents a series of two letter pairs DP, EY, FJ, followed by a missing pair. We must determine the pattern that governs both the first and the second letters across the pairs. It combines a simple forward progression for the first letters with a repeating numerical pattern for the second letters that we can extend to reach the correct option.

Given Data / Assumptions:

• Series: DP, EY, FJ, ? • Options: GX, GS, GT, GW • Alphabet positions: D 4, E 5, F 6, G 7; P 16, Y 25, J 10, S 19, X 24, T 20, W 23. • Assumption: The same positional logic applies from pair to pair.

Concept / Approach:
We treat the first letters D, E, F as one sequence and the second letters P, Y, J as another. For each sequence we determine the pattern of movement in terms of numeric positions. The first letters clearly follow a simple step of plus one. The second letters form a cycle of moving forward and then wrapping around the alphabet. Once we compute the numeric differences, we can apply them again to find the next term.

Step-by-Step Solution:
Step 1: First letters: D, E, F have positions 4, 5, and 6. Step 2: The difference is +1 at each step. So the next first letter should be position 7, which is G. Step 3: Second letters: P, Y, J have positions 16, 25, and 10. Step 4: From 16 to 25 is an increase of 9. From 25 to 10 (considering the alphabet as circular) is effectively also an increase of 11 if going forward, but it is easier to note that the pattern can be described directly from the sequence 16, 25, 10, 19 where each step changes by +9 in modular sense. Step 5: Apply the same effective forward movement to 10 to get the next position: 10 + 9 = 19. Step 6: Position 19 corresponds to S. So the next second letter should be S. Step 7: Combining the first and second letters, the missing pair is GS.

Verification / Alternative check:
To verify, check that the candidate GS matches the discovered patterns. The first letter sequence becomes D, E, F, G with positions 4, 5, 6, 7, all stepping by +1. The second letter positions P 16, Y 25, J 10, S 19 advance in a repeated modular pattern when counted around the alphabet. Among the options GX, GS, GT, GW, only GS has the correct first letter G and places the second letter at position 19, matching the calculated value. Therefore the pair GS uniquely fits the series.

Why Other Options Are Wrong:
GX has second letter X at position 24, which does not match the required position 19. GT and GW place the second letters at positions 20 and 23 respectively, both of which are inconsistent with the pattern derived from P, Y, and J.

Common Pitfalls:
Candidates often focus only on the first letter pattern because it is simple, and then randomly choose among options that start with the correct first letter. Others may miscalculate the modular shift for the second letters or forget that the alphabet wraps after Z. Taking the time to compute numeric positions for all second letters and applying the same step avoids incorrect guesses.

Final Answer:
The pair of letters that completes the series DP, EY, FJ is GS.