In the following letter series reasoning question, select the odd group of letters from the given alternatives: RTVX, GIKM, DFIK and LNPR.

Introduction / Context:
This aptitude question belongs to the category of odd letter group or odd man out in alphabet series. You are given four groups of letters RTVX, GIKM, DFIK and LNPR. Your task is to identify which group of letters does not follow the same alphabetic pattern as the other three. These types of questions test your ability to work with alphabetical positions and to recognize regular jumps between letters.

Given Data / Assumptions:

• Letter groups: RTVX, GIKM, DFIK and LNPR.
• We consider the English alphabet positions A = 1, B = 2, ..., Z = 26.
• Exactly one group does not follow the common pattern present in the remaining three groups.
• No external knowledge is required, only alphabetical order and differences between positions.

Concept / Approach:
The standard approach in such questions is to convert each letter to its numerical position and examine the differences between consecutive letters inside the same group. If three of the groups show a consistent pattern of equal jumps, and one group breaks that regularity, then that inconsistent group is the odd one out. Here, we will focus on whether the differences between consecutive letters are the same within each group, especially checking for a constant step of plus two positions.

Step-by-Step Solution:
Step 1: Consider RTVX.R = 18, T = 20, V = 22, X = 24. The differences are 18 to 20 = +2, 20 to 22 = +2, 22 to 24 = +2. So RTVX follows a +2, +2, +2 pattern.Step 2: Consider GIKM.G = 7, I = 9, K = 11, M = 13. Differences: 7 to 9 = +2, 9 to 11 = +2, 11 to 13 = +2. GIKM also follows a +2, +2, +2 pattern.Step 3: Consider LNPR.L = 12, N = 14, P = 16, R = 18. Differences: 12 to 14 = +2, 14 to 16 = +2, 16 to 18 = +2. LNPR again follows the same +2 pattern.Step 4: Consider DFIK.D = 4, F = 6, I = 9, K = 11. Differences: 4 to 6 = +2, 6 to 9 = +3, 9 to 11 = +2. The step sizes are +2, +3, +2, which breaks the constant step of +2 seen in the other three groups.Step 5: Conclude which group is odd.Only DFIK has unequal jumps between its letters, so DFIK is the odd letter group out.

Verification / Alternative check:
You can also look at each group as a shortened arithmetic progression over alphabet positions. RTVX, GIKM and LNPR are like arithmetic progressions with common difference 2 between each term. DFIK fails to behave like a pure arithmetic progression because one of its jumps is +3 while the rest are +2. This mismatch confirms that DFIK does not share the same structural rule, which is exactly what an odd one out question is designed to highlight.

Why Other Options Are Wrong:
RTVX: All letters are two positions apart, so it perfectly fits the required +2 step pattern.
GIKM: Again every consecutive pair of letters is separated by two positions, matching RTVX and LNPR.
LNPR: Follows the same regular step of +2 between all letters and therefore is not the odd group.

Common Pitfalls:
Candidates sometimes focus only on the first and last letters or on whether the letters form any meaningful abbreviation. For this type of reasoning question, meaning is not important; the pattern of movement in the alphabet is what matters. Another error is checking only the first two jumps and not verifying the entire sequence. Always compute every difference so that hidden irregularities, like the +3 inside DFIK, are not missed.

Final Answer:
The odd group of letters is DFIK, because it does not follow the constant +2 step pattern that is clearly present in RTVX, GIKM and LNPR.