Select the related group of letters from the given alternatives: DFH : GIK :: MOQ : ?

Introduction / Context:
This is a letter series analogy where each letter is shifted by a constant amount. The pair DFH : GIK shows a uniform forward shift in the alphabet. You must apply the same shift to MOQ and select the resulting group from the given options. These problems reinforce basic alphabet position skills.

Given Data / Assumptions:
- A = 1, B = 2, ..., Z = 26 is used for letter positions.
- DFH and GIK are related through a consistent transformation applied to each letter.
- MOQ must be transformed with the same rule.
- Only one option among PRT, OQS, QSU, and LNP will follow the pattern exactly.

Concept / Approach:
We identify the position of each letter in DFH and GIK, then compute the numerical difference. If the difference is constant for all positions, this difference becomes our rule. We then apply this same difference to each letter of MOQ and look for a matching option. This letter shift technique is a standard method for alphabet based analogies.

Step-by-Step Solution:
Step 1: Convert DFH to positions. D = 4, F = 6, H = 8. Step 2: Convert GIK to positions. G = 7, I = 9, K = 11. Step 3: Calculate differences. 4 to 7 is +3, 6 to 9 is +3, 8 to 11 is +3. The rule is therefore "add 3" to every letter. Step 4: Convert MOQ to positions. M = 13, O = 15, Q = 17. Step 5: Apply the +3 shift. 13 + 3 = 16 (P), 15 + 3 = 18 (R), 17 + 3 = 20 (T). Step 6: This gives the group PRT, which matches option A.

Verification / Alternative check:
To verify, subtract 3 from P, R, and T. P (16) minus 3 gives M (13), R (18) minus 3 gives O (15), and T (20) minus 3 gives Q (17). We recover MOQ, which confirms that the rule has been applied correctly. No other option, when shifted backward by 3 in each position, will produce MOQ, so PRT is uniquely correct.

Why Other Options Are Wrong:
Option B "OQS" results from adding 2, 2, and 2 to M, O, and Q instead of 3, so it does not follow the established rule.
Option C "QSU" would require different and inconsistent shifts, not a constant +3.
Option D "LNP" involves moving letters backward from M, O, Q rather than forward, again violating the established pattern.

Common Pitfalls:
A frequent error is guessing based on partial similarity, such as recognizing that the first letter P comes after M and selecting an option without checking the remaining positions. The key in sequence questions is consistency: the same shift must apply to all letters across the pair.

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