Select the related group of letters from the given alternatives: ADFG : KNPQ :: DGIJ : ?

Introduction / Context:
This is a letter based coding analogy problem where each letter is shifted by a constant amount. The pair ADFG : KNPQ is formed by applying a fixed forward shift to every letter. You must apply the same shift to DGIJ and then choose the resulting group from the options. This problem tests your consistency in handling multiple letter transformations at once.

Given Data / Assumptions:
- Alphabet positions range from A = 1 to Z = 26.
- ADFG and KNPQ are related through an identical operation applied to each letter.
- DGIJ must undergo the same operation to get the answer group.
- Only one of NORS, NPQS, NQST, and NQTU correctly reflects the transformed letters.

Concept / Approach:
We convert letters from ADFG and KNPQ to their position numbers, find the numerical difference for each corresponding pair, and check whether the difference is a constant. If it is, that difference represents the coding rule. Then we apply this fixed shift to each letter of DGIJ and compare the resulting letters with the options provided.

Step-by-Step Solution:
Step 1: Convert ADFG into positions. A = 1, D = 4, F = 6, G = 7. Step 2: Convert KNPQ into positions. K = 11, N = 14, P = 16, Q = 17. Step 3: Calculate the differences: 1 to 11 is +10, 4 to 14 is +10, 6 to 16 is +10, and 7 to 17 is +10. So the rule is "add 10" to each letter. Step 4: Convert DGIJ into positions. D = 4, G = 7, I = 9, J = 10. Step 5: Apply the +10 shift. 4 + 10 = 14 (N), 7 + 10 = 17 (Q), 9 + 10 = 19 (S), 10 + 10 = 20 (T). Step 6: This yields NQST, which matches option C.

Verification / Alternative check:
To verify, subtract 10 from NQST and check whether we get back DGIJ. N (14) minus 10 is D (4), Q (17) minus 10 is G (7), S (19) minus 10 is I (9), and T (20) minus 10 is J (10). This confirms that the forward shift of +10 and the backward shift of -10 are consistent and that we have applied the rule correctly.

Why Other Options Are Wrong:
Option A "NORS" has letters N and O which do not match the S and T created by the +10 rule for the third and fourth positions.
Option B "NPQS" changes the second and third letters incorrectly compared to the required mapping.

Common Pitfalls:
Some candidates try to solve such problems by inspecting only the first or last letters and then guessing the answer. Because many options share similar starting letters, this can cause confusion. It is essential to follow through for all letters and confirm that one constant shift explains every position in the pair.

Final Answer:
The correct related group of letters is NQST.