In the mixed letter series SCD, TEF, UGH, ____, WKL, which group of three letters should correctly fill the blank to continue the alphabetic pattern?

Introduction / Context:
This question is a typical example of a letter series where each term consists of several letters. The pattern is usually based on how each position in the group changes from term to term. To solve it, you need to identify the consistent rule for the first, second, and third letters separately and then extend that rule to fill the missing term correctly.

Given Data / Assumptions:
Given series: SCD, TEF, UGH, ____, WKL.
Each element is a group of three letters.
We assume standard alphabetical positions from A as 1 to Z as 26.
Our task is to find the missing three letter group that fits between UGH and WKL.

Concept / Approach:
The useful strategy is to examine each column of letters separately: first letters together, second letters together, and third letters together. Often each column follows a simple arithmetic progression with a fixed increment. Once we establish how each position moves, we can calculate the letters for the missing group in a systematic way.

Step-by-Step Solution:
Step 1: List the first letters: S, T, U, ?, W. In numeric form: S is 19, T is 20, U is 21, W is 23. Step 2: The movement from S to T to U is plus one each time. To go from U to the missing first letter we also add one, which gives V. To go from V to W we then add one again, which is consistent with the pattern. Step 3: List the second letters: C, E, G, ?, K. In numbers: C is 3, E is 5, G is 7, K is 11. The differences from C to E and E to G are plus two. So after G we expect plus two to get I. From I to K is also plus two, which fits. Step 4: List the third letters: D, F, H, ?, L. In numbers: D is 4, F is 6, H is 8, L is 12. The differences from D to F and F to H are plus two. After H, plus two gives J. From J to L is again plus two. Step 5: Combine the three calculated letters: first V, second I, third J. The missing group is therefore VIJ.

Verification / Alternative check:
We can now rewrite the full series as SCD, TEF, UGH, VIJ, WKL. For the first letters we have S, T, U, V, W which increases steadily by one. For the second letters we have C, E, G, I, K which increases by two each time. For the third letters we have D, F, H, J, L which also increases by two. All three positions follow consistent and simple arithmetic patterns. This confirms that VIJ is the correct missing term.

Why Other Options Are Wrong:
UJI: The first letter U breaks the pattern of S, T, U, V, W by repeating U instead of moving forward to V.
XLM: The first letter X would skip the natural next letter V, and the second and third letters do not match the established difference pattern.
DOP and STU: These groups do not maintain the same arithmetic progressions in any of the positions and are not aligned with the series structure.

Common Pitfalls:
One common mistake is to look only at the first letters and guess the missing group without checking the other positions. Another pitfall is to miscalculate letter positions in the alphabet or to forget that each column can follow its own pattern. Always cross check all three positions before choosing your final answer.

Final Answer:
The group of letters that correctly fills the blank is VIJ.