In the letter series JAK, KBL, LCM, MDN, ?, which three-letter group should replace the question mark to continue the pattern?

Introduction / Context:
This letter series question uses three-letter groups where each position follows a simple rule. Your task is to identify patterns in the first, second, and third letters separately and then combine those patterns to find the correct missing group. Such structured patterns are common in exam series questions.

Given Data / Assumptions:
- The given groups are: JAK, KBL, LCM, MDN, ?- Each term consists of three capital letters.- The pattern is likely to be consistent and based on alphabet positions.

Concept / Approach:
The best strategy is to treat each letter position independently. Map each letter to its alphabetical index (A = 1, B = 2, ..., Z = 26) and then check how the indices change from term to term. Most such series show constant increments or decrements, making it easier to extend the pattern to find the missing term.

Step-by-Step Solution:
- First letters: J, K, L, M correspond to 10, 11, 12, 13.- This is a simple +1 sequence, so the next first letter should be 14, which is N.- Second letters: A, B, C, D correspond to 1, 2, 3, 4.- This is also a +1 sequence, so the next second letter should be 5, which is E.- Third letters: K, L, M, N correspond to 11, 12, 13, 14.- Continuing the +1 pattern, the next third letter is 15, which is O.- Combining these, the missing term is N (first), E (second), O (third), giving NEO.

Verification / Alternative check:
- Check the full extended series: JAK, KBL, LCM, MDN, NEO.- All three positions follow a +1 progression through the alphabet.- Since the logic is consistent and simple, NEO is confirmed as the correct continuation.

Why Other Options Are Wrong:
- MEN, NEM, OEP all violate at least one of the three positional patterns.- MEN would require the first letter to jump from M to M again, breaking the +1 rule.- NEM and OEP disrupt the clearly increasing second and third letter sequences.- Only NEO matches the +1 increment in each of the three positions.

Common Pitfalls:
Some test takers try to treat each three-letter block as a whole and attempt to guess the answer by visual similarity alone. Others may miscount alphabet positions or forget to check every position. Always convert letters to numbers and verify each column of letters separately for such questions.

Final Answer:
The correct three-letter group that completes the series is NEO, so the correct option is NEO.