In the letter triplet series PRQ, NPO, LNM, ?, HJI, which of the following triplets correctly fills the blank to continue the pattern?

Introduction / Context:
This question deals with a sequence of three letter groups: PRQ, NPO, LNM, followed by a missing triplet, and then HJI. The task is to find the missing triplet that keeps the pattern consistent. Many such problems involve simple arithmetic steps in the alphabet for each position of the triplets. When all three letters in each successive term shift by the same amount, the logic can be discovered and extended to fill the missing entry.

Given Data / Assumptions:

• Given triplets: PRQ, NPO, LNM, ?, HJI.
• Alphabet positions: A 1 to Z 26.
• We must find the missing triplet from options IJK, KMK, JLK, JJK, ILK.

Concept / Approach:
The best strategy is to look at alphabetical positions of each letter in the triplets and examine how they change from one triplet to the next. If all three letters of each triplet move by a fixed negative or positive number, the pattern may be uniform decrement or increment. Once the step size is identified, we apply it repeatedly to find the missing triplet and confirm that the final term HJI fits naturally after it.

Step-by-Step Solution:
Step 1: Convert letters in PRQ to positions: P 16, R 18, Q 17. Step 2: Convert letters in NPO to positions: N 14, P 16, O 15. Step 3: Observe the differences from PRQ to NPO: 16 to 14 is minus 2, 18 to 16 is minus 2, and 17 to 15 is minus 2. So every letter decreases by 2 positions. Step 4: Convert LNM to positions: L 12, N 14, M 13. Again, from NPO (14, 16, 15) to LNM (12, 14, 13) the reduction is minus 2 for each letter. Step 5: Continue this pattern. Subtract 2 from each letter in LNM. For L 12, subtract 2 to get 10 which is J. For N 14, subtract 2 to get 12 which is L. For M 13, subtract 2 to get 11 which is K. Step 6: Thus, the missing triplet should be J, L, K, forming "JLK". Step 7: For completeness, verify the step from JLK to HJI. Positions J 10, L 12, K 11 go to H 8, J 10, I 9. Again, each change is minus 2, confirming that "JLK" fits perfectly between LNM and HJI.

Verification / Alternative check:
Write the full extended sequence with numeric positions: PRQ (16,18,17), NPO (14,16,15), LNM (12,14,13), JLK (10,12,11), HJI (8,10,9). We see a clean chain where each triplet is obtained by subtracting 2 from every letter of the previous triplet. No other option, when inserted, would allow the same minus 2 pattern to continue without interruption. This confirms that JLK is the correct missing element.

Why Other Options Are Wrong:
"IJK" corresponds to positions (9,10,11); inserting it would not maintain the constant minus 2 step between LNM and HJI.
"KMK" mixes letters in a way that would break the uniform decrement pattern across all three positions.
"JJK" has duplicate letters and would not maintain the correct spacing or symmetry between neighbouring triplets.
"ILK" deviates from the exact minus 2 requirement and results in uneven changes across different letter positions.

Common Pitfalls:
Some candidates attempt to find patterns based only on the first letters or on the visual appearance of the triplets, ignoring consistent numeric differences. Others may check only one transition instead of verifying all transitions in the series. A reliable method is always to convert letters to numbers, compute differences, and confirm that the rule holds at every step before choosing an answer.

Final Answer:
The missing triplet that correctly continues the pattern is JLK.