A series of three letter groups is given with one term missing. Select the alternative that completes the pattern: WFB, TGD, QHG, ?

Introduction / Context:
Here we have a sequence of three letter clusters that change in a structured way. You are asked to identify the next cluster that continues the pattern. Solving this problem requires tracking how each individual letter moves across the series and confirming that a single logical rule fits all three positions.

Given Data / Assumptions:

• Given groups: WFB, TGD, QHG, ? • Alphabet positions: A = 1, ..., Z = 26. • The first letters form one sequence, the second letters another, and the third letters a third sequence. • The rule should be arithmetic in nature and applied consistently.

Concept / Approach:
We treat each letter position as a separate numeric sequence. By converting letters to numbers, we can see whether the changes are constant additions, constant subtractions, or gradually changing steps. When the first, second, and third letter sequences all fit the same type of pattern, the next term can be determined reliably.

Step-by-Step Solution:
Step 1: Analyze the first letters: W, T, Q. Positions: W = 23, T = 20, Q = 17. Differences: 23 → 20 is −3, 20 → 17 is −3, so we subtract 3 each time. Next first letter: 17 − 3 = 14, which is N. Step 2: Analyze the second letters: F, G, H. Positions: F = 6, G = 7, H = 8. Differences: 6 → 7 is +1, 7 → 8 is +1, so we add 1 each time. Next second letter: 8 + 1 = 9, which is I. Step 3: Analyze the third letters: B, D, G. Positions: B = 2, D = 4, G = 7. Differences: 2 → 4 is +2, 4 → 7 is +3. The increment is increasing by 1. Next increment: +4, so 7 + 4 = 11, which is K. Step 4: Combine the letters to obtain the next term: NIK.

Verification / Alternative check:
Confirming the pattern: first letters follow −3 steps (23, 20, 17, 14), second letters follow +1 steps (6, 7, 8, 9), and third letters follow +2, +3, +4 (2, 4, 7, 11). The letter K is position 11, which fits this pattern. No other option satisfies all three sequences simultaneously.

Why Other Options Are Wrong:
• NIL: The third letter L is 12, which does not match the +4 step from 7. The second letter I is correct, but the third letter is too large by one position. • NLK: The second and third letters L and K do not result from the +1 and growing increment pattern observed in the series. • NJL: Here both J and L break the carefully established numeric differences in the second and third letter sequences.

Common Pitfalls:
One pitfall is to look for a single constant step affecting all three positions, which is not the case here. Another is to focus on only two positions and ignore the third. Alphabet pattern questions often use slightly different rules across positions, so it is crucial to verify each letter column.

Final Answer:
The correct group that completes the series is NIK.