Find the next term in the letter series: YEB, WFD, UHG, SKI, ( ? ). Use column-wise shifts: first letters −2 each step, seconds +1, +2, +3, +4…, thirds alternate +2, +3, +2, +3…

Introduction / Context:
Three-letter series often encode separate arithmetic progressions in each letter position, including alternating increments.

Given Data / Assumptions:

• Terms: Y E B; W F D; U H G; S K I; next = ?
• Indices: A=1 … Z=26; wrap-around permitted conceptually.

Concept / Approach:
Analyze each column: 1st letters step backward by 2; 2nd letters increase with growing increments; 3rd letters alternate +2, +3.

Step-by-Step Solution:

Verification / Alternative check:
Reconstructing backwards from QOL recovers the same increments, confirming consistency.

Why Other Options Are Wrong:
TOL breaks the −2 pattern in the first column; QGL/QNL do not satisfy the +4 or alternating +3 requirement.

Common Pitfalls:
Assuming constant steps in the second/third columns; here, one column has growing steps, another alternates.

Final Answer:
QOL.